WO2001001081A1

WO2001001081A1 - Flowmeter

Info

Publication number: WO2001001081A1
Application number: PCT/JP2000/004165
Authority: WO
Inventors: Yasuhiro Umekage; Yukio Nagaoka; Osamu Eguchi; Shuji Abe; Yuji Nakabayashi; Kenzo Ohji; Fumikazu Shiba; Akihisa Adachi; Masahiko Hashimoto; Toshiharu Sato; Yuji Fujii
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 1999-06-24
Filing date: 2000-06-23
Publication date: 2001-01-04
Also published as: US6915704B2; EP1243901A4; US6796189B1; US20050000301A1; KR100487690B1; US7082841B2; US20040261539A1; CN1293369C; AU5569300A; EP1243901A1; US20040267464A1; CN1358270A; US6941821B2; KR20020019929A

Abstract

To solve the problems, a flowmeter comprises transmitting/receiving means adapted for transmission/reception using the variation of the state of a fluid and provided in a passage, repeating means for repeating the transmission and reception, time measuring means for measuring the propagation time repeated by the repeating means, a flow rate measuring means for measuring the rate of flow according to the value measured by the time measuring means, and number-of-repetitions changing means for changing the number of repetitions to a predetermined number. The influence of the variation of the flow can be suppressed by changing the number of repetitions to a number suitable for the variation, and thus stable flow rate measurement with high accuracy is possible.

Description

Description Flow meter

Technical field

The present invention relates to a flow meter for measuring a flow rate of a liquid or a gas, and to a means for measuring a flow rate value accurately even when there is a pressure fluctuation or a temperature change. Background art

Conventionally, a flow meter of this type is known, for example, from Japanese Patent Application Laid-Open No. Hei 9-150006. As shown in FIG. 64, a predetermined first sampling is performed from an analog flow sensor 1 that measures a gas flow rate. A sampling program 2 for reading the measured value at each time, a gas consumption calculation program 3 for calculating the gas consumption flow rate at a predetermined time, and an analog flow sensor for the second sampling time within the predetermined time during the first sampling time. It consists of an average value calculation program 4 that reads out measured values and calculates the average value, a pressure fluctuation period estimation program 5 that estimates the period of pressure fluctuations from the output of the flow sensor, and a RAM 6 as memory. Was. Here, 7a is a CPU that executes the program, and 7b is a ROM of a memory that stores the programs. With this configuration, the measurement processing is performed so that the predetermined measurement time is at least one cycle of the oscillation cycle of the pump or a multiple of the cycle, and fluctuations in the flow rate are suppressed by averaging.

Further, as another conventional example, one disclosed in Japanese Patent Application Laid-Open No. 10-197303 is known. As shown in Fig. 65, the flow rate detection means 8 for detecting the flow rate, the cycle detection means 9 for detecting the fluctuation cycle of the flow, and the measurement time change for setting the measurement time for the flow rate detection to almost an integral multiple of the above cycle This is a configuration including means 10. Here, 11 is a flow rate calculating means, 12 is a measurement starting means, 13 is a signal processing means, and 14 is a flow path. With this configuration, the flow rate is measured according to the cycle of the fluctuation waveform, and accurate flow rate measurement is performed in a short time. Is Umono.

Further, as another conventional example, one disclosed in Japanese Patent Application Laid-Open No. 11-44563 is known. As shown in Fig. 66, the flow rate detection means 15 for detecting the flow rate, the fluctuation detection means 16 for detecting the fluctuation waveform of the fluid, and the measurement of the flow rate detection means near the zero of the AC component of the fluctuation waveform The configuration is provided with a pulsation measuring means 17 to be started and a flow rate calculating means 18 for processing a signal of the flow rate detecting means. Here, 19 is a signal processing circuit, 20 is a timing circuit, 21 is a trigger circuit, 22 is a transmission circuit, 23 is a comparison circuit, 24 is an amplification circuit, 25 is a switch, and 26 is measurement. A start signal circuit, 27 is a starting means, and 28 is a flow path. With this configuration, the flow rate around the average of the fluctuation waveform is measured, and accurate flow rate measurement is performed in a short time.

Further, as another conventional example, one as disclosed in Japanese Patent Application Laid-Open No. 8-271313 is known. As shown in Fig. 67, it is checked whether or not the flow rate value detected by the flow sensor measurement (29) is present (30). Continue. Then, if there is a flow rate, it is determined whether or not the flow rate Q is equal to or more than a specified value (31). If the flow rate is equal to or more than the specified value, it is determined whether the pressure fluctuation exceeds a predetermined value C f (3 2 ). If the pressure fluctuation does not exceed the predetermined value C f, measurement 34 is performed with a piezoelectric film sensor of a full-id flow meter. If the pressure fluctuation exceeds the predetermined value C f, it is determined whether the pressure fluctuation exceeds the second specified value (33). If the pressure fluctuation exceeds the second specified value, the piezoelectric film sensor of the Fluidec flow meter is determined. Perform measurement (3 4) with. If the value is less than the second specified value, measurement (29) is performed using a flow sensor.

Also, as shown in Fig. 68, the ultrasonic transducers 51 and 52 are installed in the flow rate measuring section 50 in the direction of the flow, and the control section 53 simultaneously starts the The transmission signal is output to the drive circuit 55. Ultrasonic waves are transmitted from the ultrasonic transducer 51 receiving the output of the drive circuit 55, and received by the ultrasonic transducer 52. Then, the reception detection circuit 56 receiving the output of the ultrasonic transducer 52 detects the ultrasonic wave and stops the timer 54. Let it. By this operation, the time (t 1) from when the ultrasonic wave is transmitted from the ultrasonic vibrator 51 to when it is detected by the ultrasonic vibrator 52 is measured. Next, the switching circuit 58 is operated by the signal of the control unit 53, the drive circuit 55 is connected to the ultrasonic transducer 52, and the reception detection circuit 56 is connected to the ultrasonic transducer 51. In this state, transmission and reception of the ultrasonic wave are performed again, and the time (t 2) from when the ultrasonic wave is transmitted from the ultrasonic vibrator 52 to when the ultrasonic wave is detected by the ultrasonic vibrator 51 is measured. Based on these two propagation times (t 1) and (t 2), the calculation unit 57 calculates the flow rate from the reciprocal difference of the propagation times.

As a conventional example of this type of flow meter, there has been known one as disclosed in Japanese Patent Application Laid-Open No. 6-269528.

However, in the first reference of the prior art described above, the gas flow rate is measured using the average value, and a long-term measurement is required to obtain a stable average value. Was. Also, in the second reference, there was a problem that it was not possible to adapt when the period fluctuated. Further, in the third and fourth references, the method of measuring the flow rate is changed without pressure fluctuation, and there is a problem that it is necessary to provide two means, a pressure measuring means and a flow measuring means. In the first to fourth references, there was a problem that when an abnormality occurred in the measurement, the measurement could not be performed or the measurement was performed with reduced accuracy.

However, in the above-described conventional configuration, if noise synchronized with the measurement period or the transmission period of the ultrasonic wave is present during reception, if the propagation time is the same, the same phase will always be multiplied during reception. There was a problem that accurate measurement was not possible. Furthermore, when the propagation time fluctuates due to temperature fluctuations and the like, the phase to be superposed changes, and the measurement error fluctuates, making it impossible to keep the correction value constant. In addition, since the measurement resolution is determined by the resolution of the timer 54, simply averaging the measured values does not increase the measurement accuracy. Is it necessary to increase the resolution of the timer 54 to perform measurements that require resolution? is there. If the operating clock of the timer 54 is set to a high frequency, problems such as an increase in current consumption, an increase in high-frequency noise, and an increase in the size of the circuit will occur. There was a problem of improving the measurement accuracy by realizing high resolution in timer measurement that operates at a low frequency.

In the fifth reference, a delay means is inserted between the control unit and the drive circuit, and the influence of the reflected wave is reduced by changing the amount of delay to avoid the reflected wave. There was a problem that the fluctuation of the reception detection time caused by the vibration of the ultrasonic transducer on the receiving side vibrating due to the noise and the reverberation of the vibration and the ultrasonic reception signal could not be reduced.

The present invention solves the above-mentioned problems, but with φ, without using a new fluctuation detection device, detects the fluctuation period softly and changes the number of repetitions repeatedly, so that it is optimal according to the flow fluctuation The first objective is to be able to set a sufficient number of repetitions, and to accurately measure a stable and measured flow rate in a short time even when there is a change in pressure or a fluctuation cycle. The second purpose is to switch the transmission and reception means to detect fluctuations without using a new fluctuation detection device, and to perform highly accurate flow measurement instantaneously by performing measurement processing synchronized with fluctuations. are doing. The third objective is to perform high-precision flow measurement even when an abnormality occurs in the measurement process by quickly detecting the abnormality by the measurement monitoring means and processing the measurement accurately. The fourth object is to perform stable and accurate flow rate measurement in a short time by using instantaneous flow rate measuring means and digital filter means. The fifth object is to measure the flow rate value accurately even when there is temperature fluctuation. Disclosure of the invention

In order to solve the above problems, the present invention provides a transmitting / receiving means provided in a flow path for transmitting and receiving using a change in the state of a fluid, a repeating means for repeating the transmission and reception, and a propagation time repeated by the repeating means. It has a configuration including a time measuring means for measuring, a flow detecting means for detecting a flow rate based on the value of the time measuring means, and a number changing means for changing to a predetermined number of repetitions. Then, by changing the number of repetitions suitable for fluctuations, The effect of movement can be suppressed, and stable flow measurement can be realized with high accuracy. Further, a pair of transmission / reception means using the propagation of sound waves as a change in the state of the fluid is provided. By using sound wave transmission / reception means, sound waves can be propagated even when there is a change in the state of the fluid, and the flow rate can be measured accurately and stably by changing the number of repetitions to a value suitable for the fluctuation. be able to.

In addition, a transmission / reception means using the propagation of heat as a state change of the fluid is provided. By using the heat transmission and reception means, heat can be transmitted even when the state of the fluid changes, and the flow rate can be measured stably with high accuracy by changing the number of repetitions suitable for the fluctuation. It can be carried out.

Further, an elapsed time detecting means for detecting information on the way of the propagation time repeatedly measured by the repeating means, a cycle detecting means for detecting a cycle of the flow rate variation from the information of the elapsed time detecting means, And a frequency changing means for setting the measurement time to be substantially an integral multiple of the set period. Since no specific detection means is required and the cycle can be detected from the information on the way of the timing means before the flow rate is detected and can be set to an integral multiple of the cycle, the flow rate measurement must be performed stably and accurately. Can be.

Further, a data holding unit that holds at least one or more propagation times of repetition transmission and reception obtained by the elapsed time detection unit, and compares the data held by the data holding unit with the measured propagation time data. In this way, a configuration is provided that includes a period detecting means for detecting the period. Then, the period can be detected by holding and comparing the time information of the instantaneous moment by the data holding means.

Further, the number-of-times changing means is configured to operate at the time of predetermined processing. By performing the processing only at the time of the predetermined processing, the processing can be reduced to the minimum required, and the power consumption can be significantly reduced.

The number-of-times changing means is configured to operate each time a predetermined flow rate is measured. By performing the measurement every time the predetermined flow rate is measured, the flow rate can be measured stably and accurately even in a flow that fluctuates drastically. Also, the frequency change means is configured to be performed before the flow rate measurement processing. Since the number of repetitions is set to a predetermined number before performing the flow rate measurement, the flow rate measurement can be performed stably and accurately.

In addition, the predetermined processing is configured to perform abnormality determination means for determining an abnormality in the flow rate from the measured flow rate, and flow rate management means for managing the usage state of the flow rate from the measured flow rate. Then, by performing only the processing of the abnormality determination and the flow rate management, the processing of changing the number of times can be suppressed to a minimum, and the power consumption can be reduced.

In addition, the number of repetitions corresponding to the cycle obtained by the cycle detection means was used in the next flow measurement. Then, by using it for the next measurement, it is not necessary to repeat the measurement for detecting the period, and the power consumption can be reduced.

Further, when the measured flow rate is less than the predetermined flow rate, the number-of-times changing means is operated. By performing the processing only when the flow rate is equal to or less than the predetermined flow rate, the processing is not performed at the time of a large flow rate, and the power consumption can be reduced.

A transmitting / receiving unit provided in the flow path for transmitting / receiving a change in the state of the fluid; a timing unit for measuring a propagation time transmitted / received by the transmitting / receiving unit; and a flow rate for detecting a flow rate based on the value of the timing unit. Detecting means, fluctuation detecting means for measuring fluctuations in the flow path by the transmitting and receiving means, and measurement control means for starting measurement in synchronization with the fluctuation timing of the fluctuation detecting means. By measuring fluctuations in the flow path by the transmission / reception means, there is no need to provide a separate sensor for detecting fluctuations, so that the size can be reduced, the flow path can be simplified, and even if fluctuations occur, short The flow rate can be measured stably and accurately over time.

Further, a pair of transmission / reception means using the propagation of sound waves as a change in the state of the fluid is provided. Then, the change in the state of the fluid can be detected by the sound wave transmitting / receiving means, and by starting the measurement in synchronization with the timing of the fluctuation, the flow rate can be measured accurately and stably.

In addition, a transmission / reception means using the propagation of heat as a state change of the fluid is provided. And Fluid state changes can be detected by the heat transmission / reception means, and measurement can be started in synchronization with the timing of the fluctuations, enabling accurate and stable flow measurement. A first vibrating means and a second vibrating means provided in the flow path for transmitting and receiving a sound wave; a switching means for switching the transmitting and receiving operations of the first vibrating means and the second vibrating means; A fluctuation detecting means for detecting a pressure fluctuation in the flow path of at least one of the second vibrating means; a time measuring means for measuring a propagation time of a sound wave transmitted and received by the first vibrating means and the second vibrating means; When the output of the means changes by a predetermined amount, the time measuring means measures a first time T1 which propagates from the first vibrating means on the upstream side of the flow path to the second vibrating means on the downstream side. When the output changes in reverse to the predetermined change, the time measurement means controls the second time measurement T2 to be transmitted from the second vibration means on the downstream side of the flow path to the first vibration means on the upstream side. Control means, and the first clock time T 1 And a configuration in which a flow rate detection means for calculating the flow rate using a serial second measured time T 2. By measuring at the timing when the change in the pressure fluctuation is reversed, the phase of the pressure fluctuation and the timing of the measurement can be shifted, and the measurement error due to the pressure fluctuation can be canceled.

In addition, the measurement of the first clocking time T1 is started when the output of the fluctuation detecting means changes by a predetermined amount, and the measurement of the second clocking time T2 is started when the output of the fluctuation detecting means changes in a direction opposite to the predetermined change. Measurement control, and at the next measurement, when the output of the fluctuation detecting means changes in reverse to the predetermined change, measurement of the first time T1 is started, and when the output of the fluctuation detecting means changes by a predetermined amount. Start the measurement of the second clock time T2 The measurement control means that performs the measurement control and the second clock time T2 obtained by using the previous first clock time T1 and the second clock time T2 while alternately changing the measurement start The flow rate detecting means is configured to calculate the flow rate by sequentially averaging the first flow rate and the second flow rate obtained using the next first time measurement time T1 and second time measurement time T2. By changing the measurement timing as described above and performing the first clocking time T1 and the second clocking time T2, even if the pressure fluctuation is not symmetrical on the high pressure side and low pressure side, The effects can be offset. In addition, a repetition unit that performs transmission and reception multiple times is adopted. Then, by increasing the number of measurements, averaging can be performed, and stable flow measurement can be performed. In addition, a configuration is provided that includes a repetition unit that performs transmission and reception multiple times over an integral multiple of the fluctuation period. Then, by measuring at the fluctuation cycle, the pressure fluctuation is averaged, and a stable flow rate can be measured.

Further, there is provided a repetition means for starting transmission / reception measurement when the output of the fluctuation detection means changes by a predetermined amount, and repeatedly performing transmission / reception measurement of the sound wave until the output of the fluctuation detection means changes the same as the predetermined change. Since the start and stop of the measurement can be made to coincide with the cycle of the pressure fluctuation, the measurement can be performed at the fluctuation cycle, and the pressure fluctuation can be averaged and a stable flow rate can be measured.

In addition, the first vibration means and the second vibration means are provided with a selection means for switching between a case where the first vibration means is used for transmitting and receiving a sound wave and a case where the first vibration means is used for detecting a pressure fluctuation. Then, at least one of the first vibrating means and the second vibrating means can be used for pressure detection, and both flow rate measurement and pressure measurement can be achieved.

In addition, the configuration is provided with a fluctuation detecting means for detecting the vicinity of zero of the AC component of the fluctuation waveform. Then, by detecting the fluctuation near the zero component of the fluctuation, the range of the time for performing the flow measurement can be started from near the fluctuation zero. Measurement can be stabilized.

Further, a configuration is provided which includes a cycle detecting means for detecting a cycle of the signal of the fluctuation detecting means, and a measuring control means for starting the measurement only when the cycle detected by the cycle detecting means is a predetermined cycle. By starting the measurement only at the predetermined period, the measurement can be performed at the predetermined fluctuation, and the stable flow rate can be measured.

In addition, when a signal from the fluctuation detecting means cannot be detected, a configuration is provided in which a detection canceling means is automatically started after a predetermined time. Then, even if the fluctuation disappears, the flow rate can be automatically measured after a predetermined time.

Also, the transmitting / receiving means, the first vibrating means and the second vibrating means may be a piezoelectric vibrator. The configuration was composed of By using a piezoelectric vibrator, it is possible to detect pressure fluctuations while using ultrasonic waves for transmission and reception.

A transmission / reception unit provided in the flow path for transmitting / receiving using a change in the state of the fluid; a repetition unit for repeating the signal propagation of the transmission / reception unit; and measuring a propagation time during the repetition by the repetition unit. Time measuring means, flow rate detecting means for detecting a flow rate based on the value of the time measuring means, fluctuation detecting means for detecting fluid fluctuation in the flow path, measurement control means for controlling each of the means, and each of the means Measurement monitoring means for monitoring abnormalities in the data. If there is a fluctuation in the flow in the flow path, the flow rate is measured in accordance with the fluctuation, and the abnormality can be quickly detected by the measurement and monitoring means. The value is stable, the flow rate can be measured with high accuracy, and the reliability can be improved.

Further, a pair of transmission / reception means using the propagation of sound waves as a change in the state of the fluid is provided. By using sound waves, flow rate measurement can be performed even if the fluid fluctuates, and the measurement and monitoring means can take corrective measures when an abnormality occurs, thereby improving reliability. In addition, transmission / reception means using heat propagation as a change in the state of the fluid is provided. By using the heat propagation, the flow rate can be measured even if the fluid fluctuates, and the measurement and monitoring means can take corrective action in the event of an abnormality to improve reliability.

A pair of transmitting / receiving means provided in the flow path for transmitting / receiving a sound wave; a repeating means for repeating signal propagation of the transmitting / receiving means; and measuring a propagation time of the sound wave during the repetition by the repeating means. Time measuring means, flow rate detecting means for detecting a flow rate based on the value of the time measuring means, fluctuation detecting means for detecting fluid fluctuation in the flow path, measurement control means for controlling each of the means, and the measurement control After the instruction signal of the means, a start signal instructing the start of sound wave transmission at the time of the first output signal of the fluctuation detecting means, and an end signal instructing the repetition of transmission and reception of sound waves at the time of the second output signal of the fluctuation detecting means. And measurement monitoring means for monitoring abnormalities of the start signal and the end signal. When there is a fluctuation in the flow in the flow path, measurement is performed in synchronization with the fluctuation cycle, and the measurement and monitoring means are used. Since an abnormality can be detected, the measured value is stable and the flow rate can be measured with high accuracy. In addition, when an abnormality is taken, correct measures can be taken and the reliability of the measured flow rate value can be improved. Also, a measurement monitoring means is provided for instructing the start of sound wave transmission after a predetermined time when a start signal is not generated within a predetermined time after the instruction of the measurement control means. Then, even when there is no fluctuation and there is no start signal within a predetermined time, the flow rate can be measured every predetermined time, and data loss can be prevented.

In addition, there is provided a measurement monitoring means for instructing the start of sound wave transmission after a predetermined time when no start signal is generated within a predetermined time after the instruction of the measurement control means, and performing measurement at a predetermined number of repetitions. Even if there is no fluctuation and there is no start signal within a predetermined time, the flow rate can be measured at a predetermined number of repetitions every predetermined time, and loss of data can be prevented.

In addition, when the start signal is not generated within a predetermined time after the instruction of the measurement control means, the measurement monitoring means which does not perform the measurement until the instruction of the next measurement control means is provided. By waiting for the next measurement instruction, useless measurement can be stopped and power consumption can be reduced.

In addition, a measurement monitoring means is provided for terminating the reception of the sound wave when the end signal is not generated within a predetermined time after the start signal. Then, by forcibly terminating the measurement, the measurement does not stop waiting for the termination, and the process can proceed to the next processing, and a stable measurement operation can be performed.

In addition, when the end signal is not generated within a predetermined time after the start signal, the measurement monitoring means for terminating the reception of the sound wave and outputting the start signal again is provided. Then, by forcibly terminating the measurement, the measurement does not stop waiting for the end, and re-measurement is performed by outputting the start signal again, so that a stable measurement operation can be performed.

Also provided is a measurement monitoring means that stops transmission / reception processing when the number of repetitions becomes abnormal. Then, when the number of repetitions is abnormal, by stopping the measurement, the flow rate can be measured using only accurate data. Also, of the pair of transmission / reception means, the first number of repetitions at the time of measurement transmitted from one transmission / reception means and received by the other transmission / reception means, and transmitted from the other transmission / reception means and received by one transmission / reception means Measurement monitoring means for comparing the second number of repetitions at the time of measurement and outputting a start signal again when the difference between the two repetitions is equal to or more than a predetermined number is provided. When the number of repetitions is significantly different, remeasurement is performed, and measurement is performed in a state where the fluctuation period is stable, so that highly accurate flow rate measurement can be performed.

Also, of the pair of transmission / reception means, the first number of repetitions at the time of measurement transmitted from one transmission / reception means and received by the other transmission / reception means, transmitted from the other transmission / reception means and received by one transmission / reception means A repetition means was provided to set the second number of repetitions during measurement to be the same. With the same number of repetitions, a predetermined flow rate measurement can be performed even when the fluctuation cycle is unstable.

Also, the number of times the start signal is output again is set to a predetermined number of times, and a measurement / monitoring means is provided for monitoring such that the signal is not repeated forever. By limiting the number of re-measurements, stable processing can be performed without infinite processing. In addition, the flow rate was determined from the reciprocal difference of the propagation time measured by repeating the transmission and reception of the ultrasonic waves multiple times. By using ultrasonic waves, transmission and reception can be performed without being affected by the fluctuating frequency in the flow path, and by measuring the flow rate from the reciprocal difference of the propagation time measured by repeating transmission and reception, the cycle It is possible to measure even long-term fluctuations in units of one cycle, and the difference in propagation time due to fluctuations can be offset by the reciprocal difference.

Further, an instantaneous flow rate detecting means for detecting an instantaneous flow rate, a pulsation determining means for determining whether or not the flow rate value is pulsating, and at least one of calculating a flow rate value using means different depending on the determination result of the pulsation determining means. At least one stable flow rate calculating means is provided. Then, by determining the variation of the measured flow rate and switching the flow rate calculation means, it is possible to calculate a stable flow rate with one flow rate measurement means according to the variation amount.

In addition, instantaneous flow rate detection means for detecting instantaneous flow rate and digital filter for flow rate value The filter processing means for processing, and the stable flow rate calculating means for calculating the flow rate value by the filter processing means are provided. By performing digital filtering, arithmetic calculations equivalent to averaging can be performed without using a lot of data memory, and filter characteristics can be changed by changing one variable called a filter coefficient. can do.

Also, a stable flow rate calculating means for calculating a stable value of the flow rate value by the digital filter processing means when the pulsation determining means determines pulsation is provided. Then, at the time of pulsation, it is possible to stabilize a large pulsation by using a steep filter characteristic, and it is possible to perform a filtering process only at the time of pulsation.

Further, the pulsation determination means is configured to determine whether the fluctuation width of the flow value is equal to or greater than a predetermined value. Then, by performing the determination based on the fluctuation range of the pulsation, the filter processing can be changed according to the fluctuation range of the pulsation.

The filter processing means is configured to change the filter characteristics according to the fluctuation range of the flow value. By changing the filter characteristics according to the fluctuation range, the filter characteristics are gradual when the fluctuations are small, so that the fluctuations in the flow rate can be quickly changed. Fluctuations in the flow rate can be greatly suppressed.

Also, the filter processing is performed only when the flow rate value detected by the instantaneous flow rate detection means is low. By performing filter processing only at low flow rates, it is possible to quickly respond to flow rate changes at large flow rates and to significantly reduce the effects of pulsation at low flow rates.

The filter processing means is configured to change the filter characteristics according to the flow rate value. By changing the filter characteristics according to the flow rate value, the filter process is performed only at low flow rates to quickly respond to changes in flow rate at high flow rates and greatly reduce the effects of pulsation at low flow rates. it can.

In addition, the filter processing means is configured to filter according to the flow time interval of the instantaneous flow rate detection means. The filter characteristics are changed. By changing the filter characteristics according to the interval of the flow rate detection time, fluctuations can be suppressed by a gentle filter characteristic when the measurement interval is short and by a steep filter characteristic when the measurement interval is wide. In addition, a filter processing means is provided to change the cutoff frequency of the filter characteristics to be higher when the flow rate is large, and to change the cutoff frequency to have a lower filter characteristic when the flow rate is low. Then, the response becomes faster at a large flow rate, and the pulsation can be suppressed at a low flow rate.

Further, the filter characteristic is changed so that the fluctuation range of the flow rate value calculated by the stable flow rate calculation means is within a predetermined value. Then, by changing the filter characteristic so that the fluctuation value falls within the predetermined value, the flow rate fluctuation can always be suppressed to a predetermined value or less.

In addition, an ultrasonic flowmeter that detects the flow rate using ultrasonic waves was used as the instantaneous flow rate detection means. By using an ultrasonic flow meter, the instantaneous flow rate can be measured even when a large flow rate fluctuation occurs, and a stable flow rate can be obtained from the flow rate value by arithmetic.

A thermal flow meter was used as the instantaneous flow rate detection means. By using a thermal flow meter, the instantaneous flow rate can be measured even if a large flow rate fluctuation occurs, and a stable flow rate can be obtained from the flow rate value by arithmetic.

A flow rate measuring unit through which the fluid to be measured flows; a pair of ultrasonic vibrators provided in the flow measuring unit for transmitting and receiving ultrasonic waves; a driving circuit for driving one ultrasonic vibrator; A reception detection circuit that is connected to the ultrasonic transducer and detects an ultrasonic signal; a timer that measures the propagation time of the ultrasonic signal; a control unit that controls the drive circuit; A calculating unit for determining the driving method, and a periodicity changing unit for sequentially changing a driving method of the drive circuit, wherein the control unit changes the periodicity in the flow rate measurement so that the measuring period does not become constant. Control. For this reason, noise synchronized with the measurement cycle or the ultrasound transmission cycle Sometimes, they are not always in the same phase and are dispersed, so that measurement errors can be reduced.

A flow rate measuring unit through which the fluid to be measured flows; a pair of ultrasonic vibrators provided in the flow measuring unit for transmitting and receiving ultrasonic waves; a driving circuit for driving one ultrasonic vibrator; A reception detection circuit that is connected to the ultrasonic transducer and detects an ultrasonic signal; a control unit that receives the output of the reception detection circuit and controls the drive circuit a predetermined number of times so as to drive the ultrasonic transducer again; A controller for measuring the time, calculating a flow rate from the output of the timer by calculation, and a periodicity changing means for sequentially changing the driving method of the drive circuit, wherein the control unit controls the cycle so as not to be constant. When receiving the output of the reception detection circuit, changes the periodicity changing means for each reception detection of the reception detection circuit. Since the measurement can be performed by operating the cycle changing means with multiple settings in one flow measurement, the noise becomes a dispersion-averaged measurement result, and a stable measurement result can be obtained.

Further, the periodicity changing means is configured to switch and output output signals of a plurality of frequencies, and the control unit controls so as to change the frequency setting of the periodicity changing means and change the driving frequency of the driving circuit every measurement. By changing the drive frequency, the reception detection timing can be changed over time corresponding to the period change of the drive signal. For this reason, noise synchronized with the measurement cycle or the transmission cycle of ultrasonic waves does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

Further, the periodicity changing means is configured to output an output signal having a plurality of phases at the same frequency, and the control unit changes the phase setting of the output signal of the periodicity changing means for each measurement to change the drive phase of the drive circuit. Since control is performed to change the timing, the reception detection timing can be changed over time by converting the phase fluctuation of the drive signal into time by changing the drive phase. For this reason, noise synchronized with the measurement cycle or the transmission cycle of the ultrasonic wave does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced. Further, the frequency changing means may be configured to determine the first frequency, which is the operating frequency of the ultrasonic vibrator, and the first frequency. The control unit outputs the output signal obtained by changing the setting of the second frequency of the periodicity changing unit for each measurement via the drive circuit, with a configuration in which a signal of a second frequency different from the one frequency is superimposed and output. Therefore, the periodicity in the flow measurement can be disturbed. For this reason, noise synchronized with the measurement cycle or the transmission cycle of ultrasonic waves does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

In addition, the periodicity changing means changes the vibration of the ultrasonic transducer at the time of transmission and changes the reception detection timing by switching the setting with and without the second frequency, so that the periodicity in the flow rate measurement may be disturbed. Since the noise synchronized with the measurement cycle or the transmission cycle of the ultrasonic wave does not always exist in the same phase at the time of reception and is dispersed, the measurement error can be reduced.

In addition, the periodicity changing means changes the phase setting of the second frequency, thereby changing the vibration of the ultrasonic vibrator at the time of transmission and changing the reception detection timing. Alternatively, noise synchronized with the transmission cycle of ultrasonic waves does not always exist in the same phase at the time of reception, and is dispersed and averaged, so that measurement errors can be reduced.

Also, the periodicity changing means changes the frequency setting of the second frequency, changes the vibration of the ultrasonic transducer at the time of transmission, and changes the reception detection timing, so that the periodicity in the flow measurement can be disturbed, and the measurement cycle can be changed. Alternatively, noise synchronized with the transmission cycle of the ultrasonic wave does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

In addition, the periodicity changing means includes a delay unit capable of setting a different delay time, and the control unit changes the delay setting every time ultrasonic transmission or ultrasonic reception is detected. This makes it possible to disperse the reverberation of the transmitted ultrasonic wave and the effect of tailing of the ultrasonic transducer, thereby reducing measurement errors.

Also, since the width of the cycle changed by the cycle changing means is an integral multiple of the value corresponding to the propagation time variation due to measurement error, the error is minimized when all settings are summed and averaged. be able to.

In addition, since the width of the cycle changed by the cycle changing means is the cycle of the resonance frequency of the ultrasonic transducer, the average value of the sum of all settings is the minimum measurement error generated by the reverberation and tailing of the ultrasonic sensor. Therefore, the measurement error can be reduced. In addition, since the order of the pattern for changing the periodicity is the same for the measurement in the upstream direction and the measurement in the downstream direction, the measurement in the upstream direction and the measurement in the downstream direction are always the same condition, and the measurement when the flow rate fluctuates The result can be stabilized.

Also, since the predetermined number is an integral multiple of the number of changes of the periodicity changing means, all the set values of the periodicity changing means can be set uniformly in one flow measurement, and the measurement result is stable. Can be done.

A flow rate measuring unit through which the fluid to be measured flows; a pair of ultrasonic vibrators provided in the flow measuring unit for transmitting and receiving ultrasonic waves; a driving circuit for driving one ultrasonic vibrator; A reception detection circuit connected to the ultrasonic transducer for detecting an ultrasonic signal; a first timer for measuring a propagation time of the ultrasonic signal; and a first timer for detecting reception of the ultrasonic signal after the reception detection circuit detects the reception time. A second timer for measuring the time until the value changes, a control unit for controlling the drive circuit, and a calculation unit for calculating the flow rate from the outputs of the first timer and the second timer. And a configuration for correcting the second timer with the first timer. Then, the flow rate is calculated based on the value obtained by subtracting the value of the second timer from the value of the first timer, so that the timing resolution becomes equal to that of the second timer. Since the operation time of the second timer is very short, power consumption can be reduced, and a flowmeter with high resolution can be realized with low power consumption. In addition, accurate flow measurement can be performed if the second image stably operates until the flow measurement after the correction, so that accurate measurement can be performed even if the second image has no long-term stability. Can be. A high-precision flowmeter can be easily realized with general parts.

Also, a temperature sensor is provided, and when the output of the temperature sensor changes by more than the set value, the second The timer is corrected by the first timer. For this reason, even if the second timer changes its characteristic with respect to the temperature change, it can be corrected and accurate measurement each time a temperature change occurs. At the same time, correction is performed only when necessary, so that power consumption can be reduced.

Further, a voltage sensor for detecting a power supply voltage of the circuit is provided, and the second timer is corrected by the first timer when the output of the voltage sensor changes by a set value or more. For this reason, even if the second image has a characteristic that changes with respect to the power supply voltage change, it can be corrected and accurate measurement can be performed each time the power supply voltage change occurs. At the same time, the power consumption can be reduced because it is not necessary to perform the correction periodically. A flow rate measuring unit through which the fluid to be measured flows; a pair of ultrasonic vibrators provided in the flow measuring unit for transmitting and receiving ultrasonic waves; a driving circuit for driving one ultrasonic vibrator; A reception detection circuit that is connected to the ultrasonic transducer and detects an ultrasonic signal; a control unit that receives the output of the reception detection circuit and controls the drive circuit a predetermined number of times so as to drive the ultrasonic transducer again; The control section has a constant measurement cycle, including a timer for measuring time, a calculation section for calculating a flow rate from the output of the timer by calculation, and periodicity stabilizing means for sequentially changing a driving method of the drive circuit. The periodic stabilization means is controlled so that With this configuration, the measurement cycle is always constant even when the propagation time changes, so that the noise synchronized with the measurement cycle or the ultrasonic transmission cycle always has the same phase during reception regardless of the propagation time fluctuation. Therefore, the measurement error can be kept constant, and the flow measurement can be stabilized even with a very long noise period.

Further, the control unit has periodicity stabilizing means including a delay unit that can set a different delay time, and the control unit changes the output time of the drive circuit by switching the delay time. Since the measurement period is stabilized by changing the delay time, the measurement period can be stabilized without affecting the driving of the ultrasonic transducer. In addition, since the control unit controls the drive circuit to keep the measurement time constant, the measurement cycle can be controlled to be constant by a simple calculation without calculating the propagation time of each ultrasonic wave. . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of a flow meter according to Embodiment 1 of the present invention.

FIG. 2 is a timing chart illustrating the operation of the flowmeter.

FIG. 3 is a fluctuation waveform diagram illustrating the operation of the flow meter.

FIG. 4 is a flowchart showing the operation of the flow meter.

FIG. 5 is a flowchart showing the operation of the flow meter.

FIG. 6 is a flowchart showing the operation of the flow meter according to the second embodiment of the present invention. FIG. 7 is a block diagram of a flow meter according to Embodiment 3 of the present invention.

FIG. 8 is a flowchart showing the operation of the flow meter.

FIG. 9 is another flowchart showing the operation of the flow meter.

FIG. 10 is a block diagram of a flow meter according to Embodiment 4 of the present invention.

FIG. 11 is a flowchart showing the operation of the flow meter.

FIG. 12 is a block diagram of a flow meter according to the fifth embodiment of the present invention.

FIG. 13 is a block diagram of a flow meter according to Embodiment 6 of the present invention.

FIG. 14 is a configuration diagram of the flow meter.

Fig. 15 is a timing chart showing the operation of the flowmeter.

FIG. 16 is another timing chart showing the operation of the flow meter.

FIG. 17 is a flowchart showing the operation of the flow meter.

FIG. 18 is another flowchart showing the operation of the flow meter.

Figure 19 is another block diagram of the flow meter.

FIG. 20 is a timing chart showing the operation of the flow meter according to the seventh embodiment of the present invention. FIG. 21 is a flowchart showing the operation of the flow meter.

FIG. 22 is a timing chart showing the operation of the flow meter according to the eighth embodiment of the present invention.

FIG. 23 is a flowchart showing the operation of the flow meter.

FIG. 24 is a block diagram of a flow meter according to the ninth embodiment of the present invention.

FIG. 25 is a timing chart showing the operation of the flowmeter.

FIG. 26 is a block diagram of a flow meter according to Embodiment 10 of the present invention.

FIG. 27 is a flowchart showing the operation of the flow meter.

FIG. 28 is a timing chart showing the operation of the flow meter according to Embodiment 11 of the present invention.

FIG. 29 is a timing chart showing the operation of the flow meter according to Embodiment 12 of the present invention.

FIG. 30 is a timing chart showing the operation of the flow meter.

FIG. 31 is another timing chart showing the operation of the flow meter.

FIG. 32 is a timing chart showing the operation of the flow meter according to Embodiment 13 of the present invention.

FIG. 33 is a timing chart showing the operation of the flow meter according to Embodiment 14 of the present invention.

FIG. 34 is a flowchart showing the operation of the flow meter according to Embodiment 15 of the present invention.

FIG. 35 is a flowchart showing the operation of the flow meter according to Embodiment 16 of the present invention.

FIG. 36 is a flowchart showing the operation of the flow meter according to Embodiment 17 of the present invention.

FIG. 37 is a flowchart showing an operation of the flow meter according to Embodiment 18 of the present invention. FIG. 38 is a flowchart showing the operation of the flow meter according to Embodiment 19 of the present invention.

FIG. 39 is a flowchart showing the operation of the flow meter according to Embodiment 20 of the present invention.

FIG. 40 is a flowchart showing the operation of the flow meter according to Embodiment 21 of the present invention.

FIG. 41 is a block diagram of a flow meter according to Embodiment 22 of the present invention.

FIG. 42 is a block diagram of a flow meter according to Embodiment 23 of the present invention.

Fig. 43 is a flow chart showing the operation of the flowmeter.

FIG. 44 is a flowchart showing digital filter processing of the flow meter. FIG. 45 is a filter characteristic diagram illustrating the operation of the flow meter.

FIG. 46 is a flowchart showing the operation of the flow meter according to Embodiment 24 of the present invention.

FIG. 47 is a flowchart showing the operation of the flow meter according to Embodiment 25 of the present invention.

FIG. 48 is a flowchart showing the operation of the flow meter according to Embodiment 26 of the present invention.

FIG. 49 is a flowchart showing the operation of the flow meter according to Embodiment 27 of the present invention.

FIG. 50 is a flowchart showing the operation of the flow meter according to Embodiment 28 of the present invention.

FIG. 51 is a block diagram of a flow meter according to Embodiment 29 of the present invention.

FIG. 52 is a block diagram of a flow meter according to Embodiment 30 of the present invention.

FIG. 53 is a block diagram of the periodicity changing means of the flow meter.

Fig. 54 is a diagram showing the reception detection timing of the flow meter.

FIG. 55 is a block diagram of a flow meter according to Embodiment 31 of the present invention. FIG. 56 is a block diagram of the periodicity changing means of the flow meter.

FIG. 57A is a block diagram of a periodicity changing unit of the flow meter according to Embodiment 32 of the present invention.

FIG. 57B is a diagram showing the reception detection timing of the flow meter.

FIG. 58 is a block diagram of a periodicity changing unit of the flow meter according to Embodiment 33 of the present invention.

FIG. 59 is a block diagram of a periodicity changing means of the flow meter according to Embodiment 34 of the present invention.

FIG. 60 is a block diagram of the periodicity changing means of the flow meter according to Embodiment 35 of the present invention.

FIG. 61 is a block diagram of a flow meter according to Embodiment 36 of the present invention.

FIG. 62 illustrates operations of the first timer and the second timer according to Embodiment 36 of the present invention.

FIG. 63 is a block diagram of a flow meter according to Embodiment 37 of the present invention.

FIG. 64 is a block diagram of a conventional flow meter.

FIG. 65 is a block diagram of another conventional flow meter.

FIG. 66 is a block diagram of another conventional flow meter.

FIG. 67 is a flowchart showing the operation of another conventional flowmeter.

FIG. 68 is a block diagram of a conventional flow meter. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)

FIG. 1 is a block diagram of a flow meter according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 117 denotes a first transmission / reception means provided in the flow path 116 for transmitting / receiving using a sound wave propagation as a change in state of a fluid, and 118 denotes a second transmission / reception means as a transmission / reception means Means, 1 19 is a repetition means for repeating the signal transmission of the first transmission / reception means 117 and the second transmission / reception means 118, 120 is a sound wave during repetition by the repetition means 1 19 A time measuring means for measuring the propagation time, a flow rate detecting means for detecting a flow rate based on the value of the time measuring means, and a frequency changing means for sequentially changing the flow rate to a predetermined number of repetitions. Then, an elapsed time detecting means 1 23 for detecting information on the way of the propagation time repeated by the repeating means 1 19, and a cycle detecting means 1 for detecting a cycle of the flow rate variation from the information of the elapsed time detecting means 123. 24, and a number-of-times changing means 122 for changing the setting so that the measurement time is almost an integral multiple of the cycle detected by the cycle detecting means 124. Here, data holding means 125 holding one transmission time of each transmission and reception obtained by the elapsed time detecting means 123, and data held by the data holding means 125 and measured propagation The period is detected by the period detecting means 124 by comparing time data. Reference numeral 1 26 denotes switching means for switching the transmission / reception operation of the first vibrator 1 17 and the second vibrator 1 18, 1 2 7 denotes a transmitter for transmitting an ultrasonic signal, and 1 2 8 denotes an ultrasonic wave It is a receiver that receives a signal.

Next, the operation and action will be described with reference to FIGS. As shown in FIG. 2, in the flow meter of the present invention, measurement is started by a repetition start signal, and the input signal is input to the first vibrator, whereby the first vibrator vibrates and emits a sound wave. The sound wave is received by the second vibrator, and the propagation time during this time is measured while the time counting means is counting with a predetermined clock. The delay time in the figure is a waiting time for waiting for sound wave attenuation, and is fixed. Then, after detecting the value obtained by counting the delay time and the propagation time as C i, an input signal is again input to the first vibrator, a sound wave is transmitted, and the second vibrator receives and repeats the measurement a predetermined number of times. At this time, the count number C i +1 received at the time of the second vibration is compared with the previous C i to detect a cycle in which the flow velocity fluctuation occurs repeatedly. For example, as shown in Fig. 3, the flow velocity fluctuations V5 and V6 have a negative count value difference C5—C6, but the flow velocity fluctuations V6 and V7 have The difference C 6 — C 7 becomes a positive value and the sign is inverted. And again, Five

When the difference between the counts C i-1 C i +1 changes from a negative value to a positive value, the cycle is detected at each repetition according to the process shown in the flowchart of FIG. 4. .

The flowchart of FIG. 4 shows the flow of detecting the cycle, and shows that a change in the flow velocity fluctuation is detected by holding one clock counter and comparing it with the next clock counter. Also, as shown in Fig. 5, the processing of ① and the means for changing the number of times were configured to be performed every time before the flow rate measurement. In this way, by detecting the period and repeatedly measuring the propagation time during that period, even if there is a fluctuation in the flow, it is averaged by measuring in one period of the fluctuation, so the measurement is performed. The flow rate will be measured without being affected by fluctuations. If the measurement is performed not only for one cycle but also for multiple cycles, more stable and accurate flow rate measurement can be performed.

As for the detection of the period, the method of detecting the difference by counting the difference between the count values and inverting the sign has been described.However, the point where the difference is the largest may be detected, or the held count value and the most The cycle may be obtained by detecting a point at which a close count value is measured again. In addition, as described by comparing one piece of held data, a cycle may be obtained by using an autocorrelation or a frequency analysis method using a plurality of held data, or the period may be obtained from a plurality of held data. The period may be detected by calculating the difference as shown in FIG.

In this way, the configuration can be simplified without the need for the flow fluctuation detection means, and the cycle is detected from the intermediate information of the time measurement means before the flow rate detection, and the time of the repeated measurement is set to an integral multiple of the cycle. Therefore, flow measurement can be performed stably and accurately. The period can be detected each time by storing and comparing the instantaneous timing information by the data holding means. In addition, by changing the number of successive repetitions, the influence of a change in flow fluctuation can be suppressed, and stable flow measurement can be realized. Since the number of repetitions is set to an integral multiple of the cycle immediately before the flow rate measurement, the flow fluctuation is averaged, and the flow rate measurement can be performed stably and accurately. (Embodiment 2)

FIG. 6 is a flowchart showing the operation of the flow meter according to the second embodiment of the present invention. The difference from the first embodiment is that the number of repetitions according to the cycle obtained by the cycle detecting means is a processing configuration used at the next flow rate measurement. The configuration is shown in Fig. 1.

As shown in FIG. 6, while measuring the propagation time T1 from the first vibrator, the time information Ci of the time means at that time is held in the data holding means. Then, measurement T2 of the propagation time from the second vibrator is performed, and the flow velocity and the flow rate are calculated from T1 and T2. Then, the period of the flow fluctuation is detected from the held timing information Ci by the method described in the first embodiment, and the number of repetitions is changed and reflected in the next measurement.

In this way, by using it for the next measurement, it is possible to perform both flow measurement and cycle measurement, eliminating the need for repetitive measurement of sound wave propagation just for cycle detection, and reducing power consumption. it can. By setting the number of repetitions in accordance with the fluctuation cycle, the fluctuations are averaged, and the flow rate can be measured stably and accurately.

(Embodiment 3)

FIG. 7 is a block diagram of a flow meter according to Embodiment 3 of the present invention. The difference from the first embodiment is that the flow rate fluctuation discriminating means 12 9 for judging the magnitude of the fluctuation of the flow rate detected by the flow rate detecting means 122 1 and the flow rate fluctuation discriminated by the flow rate fluctuation determining means 1 29 And a number change means 122 for changing the number of repetitions so as to reduce the number of repetitions, and the flow rate change determination means 122 is configured to perform the determination using a standard deviation of the flow rate.

Then, as shown in the flow chart of FIG. 8, the flow rate Qi is measured. First, if the flow rate is equal to or more than a predetermined value Qm (for example, 100 liters Z time), the number of repetitions is kept as it is. If it is less than the predetermined value Qm, the standard deviation Hi is obtained based on the n data before the measured flow rate Qi. When the standard deviation Hi is equal to or greater than a predetermined value Hm (for example, 1 liter time), the number of repetitions is changed. At this time, repeated times The number is changed so as to increase from the initial value K 0 by a predetermined value d K (for example, twice). If the number of times is equal to or more than the predetermined number Km, the number is returned to the initial value and changed again.

In this way, by performing the process of changing the number of times only when the measured flow rate is less than the predetermined flow rate, it is possible to reduce the power consumption without processing when the flow rate is large. And, when the standard deviation is more than a predetermined value, the number of times is changed so that the flow rate fluctuation can be reduced. be able to. Then, the fluctuation can be detected accurately by judging the flow fluctuation using the standard deviation. In addition, by changing the number of repetitions from a predetermined number to a gradually increasing direction, the number of repetitions can be examined from a small number, so that the required number can be found in a short time.

Also, as shown in FIG. 9, by operating the repetition number changing means only when the measured flow rate is equal to or lower than the predetermined flow rate and the standard deviation is equal to or higher than the predetermined value, the number of times of changing the number of times is further restricted, thereby reducing the consumption. It can be electric power.

The method of gradually increasing the number of changes has been described.However, when the standard deviation at the time of change increases, the method of changing in the direction of decreasing increases and decreases the number of times according to the change of the standard deviation. More stable measurement can be obtained by controlling the direction of change. In addition, when the flowmeter is powered by a battery, low power consumption has the effect that the flowmeter can be used for a long time.

(Embodiment 4)

FIG. 10 is a block diagram of a flow meter according to Embodiment 4 of the present invention. The difference from the first embodiment is that an abnormality determining means 130 and a flow rate managing means 131 are provided. The number-of-times changing means is configured to operate when the abnormality determining means 130 as a predetermined process is executed and when the flow rate managing means 131 is executed.

Then, as shown in the flowchart of FIG. 11, when the abnormality determination means is executed and when the flow rate management means is executed, the number of times can be changed only when necessary. Thus, power consumption can be reduced. In other words, it is necessary to measure the flow rate in a short time due to its urgency. As a result, the abnormality determination becomes slower when the measured flow rate fluctuates due to the fluctuation of the flow, so that the measurement can be performed in a short time by changing the measurement to the number of repetitions corresponding to the fluctuation cycle. In addition, flow control is for managing what kind of load is used on the downstream side, and it is necessary to detect and determine the flow rate in a short time. The measurement can be performed in a short time by changing to the number of repetitions.

(Embodiment 5)

FIG. 12 is a block diagram of a flow meter according to the fifth embodiment of the present invention. The difference from the first embodiment is that the transmitting and receiving means uses the propagation of heat as a state change of the fluid. 1 32 is a heater for transmitting heat, and 1 33 is a temperature sensor for receiving heat. Similarly, by using the heat transmitting means and the heat receiving means, the fluctuation period can be detected from the fluctuation of the heat propagation time, so that the configuration can be simplified, and the time of the repeated measurement can be changed. The flow rate can be measured stably and accurately by setting it to an integral multiple of. In addition, the number of successive repetitions can be changed in accordance with the change in flow fluctuation, and the effect of the fluctuation can be suppressed immediately, and stable flow measurement can be realized. Since the number of repetitions is set to an integral multiple of the cycle immediately before performing the flow rate measurement, the flow fluctuation is averaged, and the flow rate measurement can be performed stably and accurately.

(Embodiment 6)

FIG. 13 is a block diagram of a flow meter according to Embodiment 6 of the present invention. In FIG. 13, reference numeral 2 23 denotes a first piezoelectric vibrator provided as a first vibrating means of a transmitting / receiving means provided in the flow path 2 24 and transmitting and receiving using ultrasonic waves as a state change of a fluid, and 2 25 A second piezoelectric vibrator as a second vibrating means of transmitting / receiving means for transmitting and receiving ultrasonic waves, a switching switch as a switching means for switching the transmitting and receiving operations of the first piezoelectric vibrator and the second piezoelectric vibrator; 227 is repeated by the first piezoelectric vibrator 222 and the second piezoelectric vibrator 222. Time-measuring means for measuring the propagation time of transmitted and received sound waves by the single round method,

228 is a flow rate detecting means for detecting a flow rate based on the value of the time measuring means, 229 is a fluctuation detecting means for measuring the pressure fluctuation in the flow path by the first piezoelectric vibrator 223 and the second piezoelectric vibrator 225, Is a measurement control unit that starts measurement in synchronization with the pressure fluctuation timing of the fluctuation detection unit.

Here, the measurement control means 230 starts measurement of the first time measurement time T1 when the output of the fluctuation detection means 229 rises, and starts measurement of the second time measurement T2 when the output of the fluctuation detection means 229 falls. During the next measurement, the measurement of the first time T1 is started when the output of the fluctuation detecting means falls, and the measurement of the second time T2 is measured when the output of the fluctuation detecting means rises. Start measurement control is performed, and the flow measurement means 228 alternates the measurement start with the first flow rate obtained using the previous first time measurement time T1 and the second time measurement time T2, and the next first time measurement value. The flow rate was calculated by successively averaging the second flow rate obtained using the clocking time T1 and the second clocking time T2. Reference numeral 231 denotes a selection switch as selection means for selecting whether to transmit / receive ultrasonic waves to the second piezoelectric vibrator or to detect pressure fluctuation, 232 denotes an ultrasonic signal transmitter, and 233 denotes an ultrasonic signal reception. 234 is a repetition means for performing sing-around measurement, and 235 is operation check means for the first piezoelectric vibrator and the second piezoelectric vibrator.

Next, the operation and action will be described with reference to FIGS. In the flow path having the configuration shown in FIG. 14, when the time T 1 for propagation from the first piezoelectric vibrator 223 to the second piezoelectric vibrator 225 is measured, T 1 = LZ (C + Vc os Θ) . When the time 時間 2 of propagation from the second piezoelectric vibrator 225 to the first piezoelectric vibrator 223 is measured, T2 = L / (C−VcosΘ). Here, V is the flow velocity in the channel, C is the speed of sound, and Θ is the inclination angle. Then, taking the reciprocal difference between Τ 1 and Τ 2, the flow velocity V is obtained from T l and Τ 2 as shown in the following equation.

l / T l-l / T2 = 2Vcos Q / \,

V = (L / 2 c 0 s (1 / T1-1 / T2) Here, if there is a pressure fluctuation in the flow path, the flow velocity changes according to the pressure fluctuation. Therefore, assuming fluctuating frequency f and fluctuating flow velocity u, Tl, Τ2 is

Τ 1 = L / (C + V c os Θ + u-s in (2 π f t))

T 2 = L / (C-Vco s Θ-u · s i n (2πf t + Y))

Becomes Here, is the time difference (phase difference) between the start of the T1 measurement and the start of the T2 measurement. And taking the reciprocal difference between T1 and T2,

1 / T 1-1 / T2

= (2 Vcos Θ

+ u-(sin (2 π ft) + sin (2 π ft +)) / L, so when ゆ = π, sin (2 π f) = — sin (2 π ft) and the effect of fluctuation Will be canceled. Therefore,

V = (L / 2 c os θ) (l / T 1-1 / T2)

As a result, the flow velocity V can be measured even during fluctuations, and the flow rate can be calculated in consideration of the cross-sectional area of the flow path. Although the above description has been given of the measurement of one transmission / reception, when the integration time is obtained by the single round method in which the propagation time is repeatedly measured by the repetition means 234, the calculation can be similarly performed by the following equation. it can.

T 1 = ∑ [LZ (C + Vc 0 s 0 + u · s i n (2 π f t i))]

= ∑L / (∑ (C + V cos 0) + ∑ (u-sin (2 π fti))) T2 = ∑ (LZ (C-Vc os Θ θ-u-sin (2 π fti + )] = ∑L / (∑ (C + V cos Θ) + ∑ (u · sin (2π fti + yu))))

Here, the subscript i indicates the number of single rounds, and ∑ indicates the integration from i = 1 to N times. Although the detailed description of the measurement process of the single round method is omitted, this is a method in which transmission and reception of ultrasonic waves are repeated to increase the total propagation time and improve measurement accuracy.

And from the reciprocal difference of T l, Τ 2 1 / T 1-1 / T 2

= (∑ [2 V c os Θ] + ∑ [ιι · (s i n (2 π f t))

+ ∑ [u-s i n (27C f t + φ))]) /) L

Then, when = π, s in (2π f t + ^)) = one s in (2π f t), and the influence of the fluctuation is canceled even if the sing-around method is used. Therefore,

V = (L / 2 c o s O) (1 / T 1-1 / T2)

As a result, the flow velocity V can be measured even during fluctuations, and the flow rate can be calculated in consideration of the cross-sectional area of the flow path.

Here, the start timing of the measurement at which the time difference becomes π will be described with reference to FIG. The output signal of the fluctuation detecting means 229 is realized by comparing and detecting the zero-cross point of the AC component of the pressure fluctuation with a comparator. That is, the T1 measurement is started at the rising edge of the output signal of the fluctuation detecting means, and the integrated time T1 is measured at a predetermined number of single rounds. On the other hand, the start of the Τ2 measurement is performed at the fall of the output signal of the fluctuation detecting means 29, and the integration time Τ2 is measured at the same predetermined number of sing-arounds. As shown in Figure 15, T1 measures the pressure waveform between A, B, and C, and T2 measures the pressure waveform between F, G, and H, which have the opposite amplitudes of A, B, and C. Therefore, the pressure fluctuation is canceled.

In addition, in the case of positive and negative symmetric pressure fluctuations as shown in Fig. 15, it can be canceled by one measurement of T1 and T2, but in the case of positive and negative asymmetry as in Fig. 16, the start of measurement can be improved. Can be canceled. That is, the start of the T1 measurement is performed at the rising edge of the output signal of the fluctuation detecting unit 229, and the integrated time T1 is measured at a predetermined number of single rounds. On the other hand, the T2 measurement is started at the fall of the output signal of the fluctuation detecting means 229, and the integrated time T2 is measured at the same predetermined number of single rounds. Then, in the next measurement, the T1 measurement is started at the falling edge of the output signal of the fluctuation detecting means 29, and the integration time T1 is measured at a predetermined number of sing-arounds. On the other hand, T2 measurement is started at the rise of the output signal of the fluctuation detecting means 229, and the integration time 時間 2 is measured at the same predetermined number of single rounds. As shown in Fig. 16, the first T1 measures between A, B, and C of the pressure waveform, and D2 measures between 0, E, and F. In this case, since C and F have different waveforms, the difference between C and F remains as an error C1 (-F), but at the time of the second measurement, T1 is measured with the inverted waveforms H, I, and J. , T 2 are measured in K, L, M. Again, J and M have different waveforms and remain as errors, but in the second measurement, M is measured from the upstream side and J is measured from the downstream side. And M remain as an error (-J-M). Then, since C = M and F = J, adding C-(-1F) and (1J-M) and taking the average results in zero and the pressure fluctuation is canceled. Become. It should be noted that when the direction of transmission and reception of ultrasonic waves is alternately inverted each time measurement is performed, it is clear that the measurement start timing may be constant. In addition, here, the measurement was explained twice, but if the waveform of the pressure fluctuation is asymmetric and complicated, the start of the measurement is changed and repeated according to the periodicity of the waveform, and the measurement is averaged. Can be minimized. Next, the flow of the measurement will be described with reference to the flowcharts of FIGS. First, it is determined whether or not the signal of the fluctuation detecting means is rising. If not, the determination is repeated until the output signal of the fluctuation detecting means 229 rises. Here, when the rise does not occur even after standing for a predetermined time, the processing as the detection canceling means stops the rise detection and measures the first time T1 and the second time T2 assuming that there is no pressure fluctuation. Do. When a rising edge is detected, the first time T1 is measured. Then, it is determined whether or not the signal of the fluctuation detecting means 229 falls. If a falling edge is detected here, the second time T2 is measured. If the falling is not detected even after standing for a predetermined time, the processing as the detection canceling means stops the falling detection, measures the second time T2 assuming that there is no pressure fluctuation, and Calculate the flow rate Q (j) from the measured time T1 and the second measured time T2.

Then, at the next measurement, as shown in Fig. 18, this time, After detecting the fall, measure the first time T1, measure the rise, measure the second time T2, and calculate the first time T1 and the second time T2. Calculate the flow rate Q (j + 1). Then, the measurement start is repeated while changing alternately, the first flow rate Q (j) and the second flow rate Q (j + 1) are measured, and the flow rate Q is calculated by successively averaging. It is averaged and the error can be eliminated in principle. As described above, since the pressure fluctuation in the flow path can be measured by the second piezoelectric vibrator 225, there is no need to provide a pressure sensor, and the size and the flow path can be simplified. Even when pressure fluctuations occur, the instantaneous flow rate can be measured stably and accurately. By measuring at the timing when the change in the pressure fluctuation is reversed, the phase of the pressure fluctuation and the timing of the measurement can be shifted, and the measurement error due to the pressure fluctuation can be canceled. By following the timing in the opposite direction each time measurement is performed, even if the pressure fluctuation is asymmetric on the high pressure side and the low pressure side, the effect of the pressure fluctuation can be offset. Then, by repeating measurements in sing-around, averaging can be performed in one measurement, and stable flow measurement can be performed. Then, by using the selecting means, at least one of the first vibrating means and the second vibrating means can be used for pressure detection, and both flow rate measurement and pressure measurement can be achieved. Then, by detecting the fluctuation near the zero component of the pressure fluctuation, the period of the fluctuation can be accurately grasped, and the flow rate can be offset. Then, even if the fluctuation disappears, the flow rate can be automatically measured after a predetermined time. By using a piezoelectric vibrator as a fluctuation detecting means, it is possible to detect pressure fluctuations while using ultrasonic waves for transmission and reception.Furthermore, there is no need to provide a dedicated pressure detecting means, and leakage can be prevented. There is an effect that a part which becomes a factor can be reduced.

Note that the same effect can be obtained functionally by detecting pressure fluctuation described in the present embodiment using a dedicated pressure detecting means. Further, the case where the second piezoelectric vibrator on the downstream side is used has been described, but the same effect can be obtained when the first piezoelectric vibrator on the upstream side is used. Furthermore, as shown in Fig. 19, the upstream and downstream piezoelectric vibrators are alternated. The same effect can be obtained by using the piezoelectric vibrator, but it is also possible to check the operating state of each piezoelectric vibrator by using them alternately. That is, when the signal of the fluctuation detecting means is a signal of the same cycle in signals from either of the piezoelectric vibrators, it can be determined that both are operating normally.

Although the flow meter is described as a general instrument, use of this flow meter as a gas meter will allow it to be used in pulsating flow piping, such as a piping system that uses a gas engine heat pump. Is possible. Furthermore, as explained in the case of pressure fluctuation, it is clear that the same effect can be obtained when there is flow rate fluctuation.

(Embodiment 7)

FIG. 20 is a timing chart showing the operation of the flow meter according to the seventh embodiment of the present invention. The difference from the sixth embodiment is that repetition means 234 for transmitting and receiving a single round a plurality of times over an integral multiple of the fluctuation period is provided. The configuration is shown in Figure 13.

As shown in FIG. 21, when the measurement is started at intervals of a predetermined time (for example, a period of 2 seconds), when the predetermined time comes, the fluctuation period detected by the fluctuation detecting means 229 is measured. Then, the number of sing-arounds substantially matching the cycle is set. For example, one propagation time can be calculated by dividing the distance between ultrasonic transducers by the speed of sound. The required number of sing-arounds can be calculated by dividing the measured period by the propagation time. The flow rate is measured repeatedly by the number of single rounds. (1) in FIG. 21 is to perform the process (2) in FIG.

Thus, by adjusting the number of sing-arounds to the fluctuation cycle, one cycle of the fluctuation can be measured, and the pressure fluctuation can be averaged and a stable flow rate can be measured. By measuring the pressure synchronization and the number of single rounds in accordance with an integral multiple of the cycle, the flow rate can be measured more stably. Furthermore, since the pressure synchronization can be detected by the signal of the piezoelectric vibrator, there is a synergistic effect that the period can be detected and the flow rate can be measured stably. FIG. 20 shows a case where two cycles are measured. If the propagation distance is short, more than a predetermined number of single rounds are required to increase the measurement accuracy.If the number of single rounds determined from the fluctuation period is smaller than the predetermined number, a multiple of the period The number of single rounds may be determined so that

(Embodiment 8)

FIG. 22 is a timing chart showing the operation of the flow meter according to the eighth embodiment of the present invention. The difference from the sixth embodiment is that the transmission / reception measurement of the sound wave is started when the output of the fluctuation detecting means 229 changes by a predetermined amount (for example, at the time of falling), and the output of the fluctuation detecting means is the same as the predetermined change. The structure is provided with a repetition means 234 that repeats the sing-around until a change (for example, at the time of a fall) is made, and performs transmission / reception measurement of sound waves. The configuration is shown in Figure 13.

As shown in Fig. 23, the rise of the fluctuation detection signal is detected at the start of measurement, and the single round is started. Then, when the signal of the fluctuation detection signal rises again, the single round is stopped and the first clock time T1 is measured. Next, at the start of measurement, the falling of the fluctuation detection signal is detected, and the sing-around is started. Then, when the signal of the fluctuation detection signal falls again, the sing-around is stopped and the second clock time T2 is measured. The flow rate is calculated from T1 and T2.

As described above, the start and stop of the measurement can be made to coincide with the cycle of the pressure fluctuation, so that the measurement can be performed at the fluctuation cycle, and the pressure fluctuation can be averaged and a stable flow rate can be measured.

(Embodiment 9)

FIG. 24 is a configuration diagram showing a flow meter according to the ninth embodiment of the present invention. The difference from the sixth embodiment is that the two-bit force counting means 2336 for counting the fluctuation of the output signal of the fluctuation detecting means 229 and the count value of the counting The measurement was performed differently between the time and the second time, and the flow rate detection means 228 was used to measure the flow rate when all the combinations of the two bits were realized the same number of times. Figure 25 shows the timing chart.

As shown in FIG. 25, when the fluctuation is repeated in two cycles, for example, the T1 measurement starts when the output of the force-measuring means is (1, 0) and the output of the fluctuation detecting means rises, and the T2 measurement is performed. Then, the measurement is started at the fall of the fluctuation detecting means. The measured flow rate at this time is conceptually expressed as Q (i) = (A-B + C) one (-B + C-D) = A + D. Then, for the next measurement, the T1 measurement starts when the output of the counting means is (1, 1) and the fluctuation detecting means falls, and the T2 measurement starts at the subsequent rising. The measured flow rate at this time is conceptually expressed as Q (i + 1) = (-B + C-D)-(C-D + A) = _ A-B. Repeated measurement in this way gives Q (i + 2) = (C-D + A)-(-D + A-B) = C + B, Q (i + 3) = (-

D + A-B)-(A-B + C) = — C— D Here, Q (i) + Q (i + 1) + Q (i + 2) + Q (i + 3) = 0, and the pressure fluctuation is canceled. In addition, although the measurement was explained four times here, if the waveform of the pressure fluctuation is asymmetric and complicated, the start of the measurement is changed and repeated according to the periodicity of the waveform, and the measurement is averaged. Can be minimized. Since measurement can be performed at all fluctuation timings, averaging is performed and the flow rate can be measured stably.

(Embodiment 10)

FIG. 26 is a configuration diagram showing a flow meter according to the fifth embodiment of the present invention. The difference from the sixth embodiment is that a cycle detecting means 237 for detecting the cycle of the signal of the fluctuation detecting means 229 and a measurement control for starting the measurement only when the cycle detected by the cycle detecting means 237 is a predetermined cycle. The configuration provided with the means 230 was adopted.

That is, as shown in FIG. 27, by starting the measurement only when the signal of the fluctuation detecting means 229 has the predetermined period Tm, the measurement can be performed at the predetermined fluctuation period even when the period fluctuates. Even in the case of the pressure waveform shown in Fig. 25, the flow rate can be measured only at a specific pressure fluctuation by detecting the period. Therefore, the pressure fluctuation Even when the period fluctuates, a stable flow rate can be measured in a short time. In addition, the detection of the period has a predetermined time width (for example, 2 milliseconds) so that the measurement is performed flexibly and the measurement is continued without interruption.

(Embodiment 11)

FIG. 28 is a configuration diagram showing a flow meter according to Embodiment 11 of the present invention. Embodiment

The difference from 6 is that the transmission / reception means uses the propagation of heat as a fluid state change. 238 is a heater for transmitting heat, 239 is a first temperature sensor for receiving heat, and 240 is a second temperature sensor for receiving heat. In addition, the second temperature sensor 240 generates heat by itself and can detect a change in the state of the fluid by a change in the self-resistance value. By using the second temperature sensor, which is a means for transmitting and receiving heat, as well, it is possible to detect a change in the state of the fluid, that is, a change in flow velocity or pressure. Then, by performing one-cycle measurement in synchronization with the detected fluctuation, the flow measurement can be performed stably and accurately as in the above-described embodiment.

(Embodiment 12)

FIG. 29 is a block diagram of a flow meter according to Embodiment 12 of the present invention. In FIG. 29, reference numeral 32 3 denotes a first piezoelectric vibrator provided as a first vibrating means of the transmitting / receiving means provided in the flow path 3 24 for transmitting and receiving using ultrasonic waves as a change in the state of the fluid; Similarly, 5 is a second piezoelectric vibrator as a second vibrating means of transmitting / receiving means for transmitting and receiving ultrasonic waves, and 326 is a switching means for switching the transmitting and receiving operations of the first piezoelectric vibrator and the second piezoelectric vibrator. All the switching switches, 327 are time-measuring means for measuring the propagation time of sound waves repeatedly transmitted and received by the first piezoelectric vibrator 323 and the second piezoelectric vibrator 325, and 328 is the time-measuring means. Flow rate detection means that measures the flow rate based on the value, 329 is a pressure fluctuation detector as a fluctuation detection means that measures the pressure fluctuation in the flow path 324, and 330 is the pressure of the pressure detector 329 Synchronous pulse output means as fluctuation detecting means for converting a signal into a digital signal; This is a measurement control unit that instructs measurement in synchronization with the timing of pressure fluctuation. Here, 3 3 2 is a transmitter of the transmitting and receiving means of the ultrasonic signal, Numeral 333 is a receiver of an ultrasonic signal transmitting / receiving means, 334 is a repeating means for repeatedly transmitting and receiving ultrasonic waves, and 335 is a measurement monitoring means for monitoring an abnormality of the measurement control means. Next, the operation and action will be described with reference to FIG. 14 and FIGS. 30 to 31. In the flow path having the configuration shown in FIG. 14, when the time T 1 of propagation from the first piezoelectric vibrator 323 to the second piezoelectric vibrator 325 is measured, T 1 = LZ (C + Vc os 0). Become. In addition, when the time T 2 that propagates from the second piezoelectric vibrator 325 to the first piezoelectric vibrator 323 is measured, T 2 = LZ (C−VcosΘ). Here, V is the flow velocity in the channel, C is the speed of sound, and 0 is the inclination angle. Then, taking the difference between the reciprocals of T 1 and Τ2, and transforming the equation, the flow velocity V is obtained from T l and Τ2 as follows.

V = (L / 2 c os θ) (l / T 1-1 / T2)

Here, if there is a pressure fluctuation in the flow path, the flow velocity changes according to the pressure fluctuation. Therefore, assuming that the pressure fluctuating frequency f and the fluctuating flow velocity u, Tl,

T l = L / (C + Vcos ^ + u-sin (2πft))

T2 = L / (C-V c os Θ-uSin (2 π f t + τ>))

Becomes Here, Yu is the time difference (phase difference) between the start of Τ1 measurement and the start of Τ2 measurement. And taking the reciprocal difference between Τ1 and Τ2,

1 / Τ 1-1 / T2

= (2 Vcos Θ

+ u-(sin (2 π ft) + sin (2 π ft + -φ)))) / L, so if = = π, sin (2 π ft + φ)) =-sin (2 ττ ft) ), And the effect of the fluctuation is cancelled. Therefore,

V = (L / 2 c os d) (1ZT 1-1ZT2)

As a result, the flow velocity V can be measured even during fluctuations, and the flow rate can be calculated in consideration of the cross-sectional area of the flow path. As described above, the measurement control means that measures the flow rate while detecting the pressure fluctuation can accurately measure the flow rate without being affected by the pressure fluctuation by setting the measurement flow rate. The above is explained with one transmission / reception measurement However, it is clear that the integration time can be obtained in the same manner when the integration time is obtained by a method of repeatedly measuring the propagation time by the repeating means 34.

Then, as shown in FIG. 30, the measurement control means 331 outputs a measurement start signal at a predetermined measurement time (for example, every two seconds), and sets a zero cross point of the pressure fluctuation as a threshold value. Wait for a change in the output signal of the synchronized pulse output means. Then, when the output signal of the synchronization pulse output means 330 outputs a falling signal of the output signal as the first output signal, measurement of the first clocking time T1 is started, and the synchronization pulse output means 330 The measurement of the propagation time is repeated until the rising signal of the output signal as the second output signal is output. In the next measurement, when the rising signal of the output signal as the first output signal of the synchronous pulse output means 330 is output, the measurement of the second clock time T 2 is started, and the synchronous pulse output means 330 The measurement of the propagation time is repeated until the falling signal of the output signal as the second output signal is output. Then, the flow rate detecting means 328 converts the time from the time T1, T2 of the time measuring means 327 to the flow rate and completes the flow rate measurement.

However, as shown in FIG. 31, the measurement control means 331 outputs a measurement start signal at a predetermined measurement time, but waits for a predetermined time for a change in the output signal of the synchronous pulse output means 330. Even if the output signal of the synchronous pulse output means does not change, a measurement start signal is automatically output and measurement is performed at a predetermined number of repetitions (for example, 256 times). For example, if the measurement interval is 2 seconds and the frequency of pressure fluctuation occurs in the range of 10 Hz to 20 Hz, the predetermined waiting time can be set between 0.1 seconds and 2 seconds. However, it is desirable to set 1 second as the optimal value. Also, the predetermined number of repetitions can be set from 2 to 5 12 times, and it is desirable to set an optimum value according to the frequency of pressure fluctuation.

In this way, even if the pressure does not fluctuate after the output of the measurement start signal, the measurement can be started after a predetermined time and the flow measurement can be performed whenever the flow measurement needs to be performed. For example, in a gas meter, etc. If no pressure fluctuation is detected at that time, the flow rate measurement can be performed automatically even when the synchronous pulse output signal is not obtained due to the pressure fluctuation, and the I can deal with it.

Although the fluctuation of the flow is explained by the fluctuation of the pressure in the flow channel, it is clear that the same effect can be obtained by using the flow velocity fluctuation detecting means even when the flow velocity varies.

(Embodiment 13)

FIG. 32 is a timing chart showing the operation of the flow meter according to Embodiment 13 of the present invention. The difference from the first and second embodiments is that, when the start signal is not generated within a predetermined time after the instruction of the measurement control means 331, measurement is not performed until the next instruction of the measurement control means. 3 to have 5 The configuration is shown in Figure 29.

As shown in FIG. 32, the measurement control means 331 outputs a measurement start signal at a predetermined measurement time. If no change in the output signal of the synchronous pulse output means appears even after waiting for a change in the output signal of the synchronous pulse output means 330 for a predetermined time, the measurement and monitoring means 335 ends the standby of the synchronous pulse signal. The measurement control means 331 is instructed to wait for the next measurement timing (for example, two seconds later). Here, if the measurement interval is 2 seconds and the frequency of pressure fluctuation occurs in the range of 10 Hz to 20 Hz, the predetermined waiting time can be set between 0.1 seconds and 2 seconds. However, it is desirable to set 1 second as the optimal value.

As described above, when the pressure does not fluctuate after the output of the measurement start signal, the standby is ended after a predetermined time and the flow measurement is not performed, so that inaccurate flow measurement can be avoided. FIG. 32 shows the timing at which the first propagation time T 1 is measured. However, when the second propagation time T 2 is measured, if no synchronization pulse occurs, the measurement time of T 1 and T 2 is measured. The measurement interval is abnormally long because the interval between them becomes abnormally long. It is possible to avoid such measurement in which the measurement accuracy is reduced. By waiting for the next measurement instruction, unnecessary measurement can be stopped and power consumption can be reduced. For example, drive a microcomputer that controls the security function with a battery, such as a gas meter. When the power is on, a long life can be achieved by reducing this power consumption.

(Embodiment 14)

FIG. 33 is a timing chart showing the operation of the flow meter according to Embodiment 14 of the present invention. The difference from the first and second embodiments is that when the end signal is not generated within a predetermined time after the start signal, the reception of the sound wave is ended, and the end signal is not generated within the predetermined time, The configuration is provided with the measurement monitoring means 335 which ends the reception of the sound wave and outputs the start signal again. The configuration is shown in Figure 29.

As shown in FIG. 33, the measurement control means 331 outputs a measurement start signal at a predetermined measurement time, and detects the first output signal when the output signal of the synchronous pulse output means falls. Start measurement. If the second output signal, at which the output signal of the synchronization pulse output means falls, does not appear after waiting for a predetermined time, the standby for the synchronization pulse signal is terminated, and a start signal is output again to perform measurement. Here, assuming that the measurement interval is 2 seconds and the pressure fluctuation frequency occurs in the range of 10 Hz to 20 Hz, the predetermined waiting time is set between 0.1 seconds and 2 seconds. Yes, but it is desirable to set 1 second as the optimal value. If it is 1 second, even if re-measurement is performed, the measurement can be completed within 2 seconds after the next measurement time. If the second output signal does not appear even after re-measurement, wait until the next measurement time.

In this way, if there is no pressure fluctuation after the start of the measurement, the standby is ended after a predetermined time and the flow measurement is not performed, so that an erroneous flow measurement can be avoided. In addition, by supplementing the re-measurement, it is possible to prevent missing of data of the predetermined periodic measurement, to smoothly perform the measurement processing such as averaging, and to improve the accuracy of the measured flow rate value. Furthermore, if the end of the measurement is not instructed, the timing means and the like will incorrectly measure, and the measurement accuracy will be reduced. It is possible to avoid such measurement in which the measurement accuracy is reduced. Then, by forcibly terminating the measurement, the measurement can be stopped without waiting for the termination, and the process can proceed to the next processing, and a stable measurement operation can be performed.

(Embodiment 15) FIG. 34 is a flowchart showing the operation of the flow meter according to Embodiment 15 of the present invention. The difference from the first and second embodiments is that when no end signal is generated within a predetermined time T after the start signal, the measurement monitoring means 3 3 5 terminates the reception of the sound wave and discards the measurement data. Was provided. The configuration is shown in Figure 29.

As shown in FIG. 34, after outputting the first output signal, a predetermined time T (for example, 0.

When the second output signal indicating the end of one cycle is not generated even after 5 seconds, the repetition of transmission and reception is terminated and the measurement data up to that point is discarded. Then, after waiting for a predetermined time, the measurement was restarted.

In this way, when measurement is not performed well, by discarding the data, only accurate data can be used and stable measurement operation can be performed. Also, there is no need to store measurement data, and the power consumption required for measurement can be reduced. In addition, by managing the predetermined time T, it is possible to manage that the periodic measurement cycle (for example, 2 seconds) has been exceeded, and to perform measurements so that the measurement timings do not overlap. it can. Then, even when the propagation time of the ultrasonic wave changes due to a change in temperature, it can be managed with the same predetermined time T.

(Embodiment 16)

FIG. 35 is a flowchart showing the operation of the flow meter according to Embodiment 16 of the present invention. The difference from the first and second embodiments is that, when the number of repetitions becomes equal to or more than a predetermined number N1, the configuration is provided with measurement monitoring means 335 for terminating the reception of the sound wave and discarding the measurement data. The configuration is shown in Figure 29.

As shown in FIG. 35, after the first output signal is output, the second output signal indicating the end of one cycle is not generated even when the number of times exceeds a predetermined number N 1 (for example, 5 1 2 times). It was decided to end the repetition of transmission and reception and discard the measurement data up to that point. Then, after waiting for a predetermined time, the measurement was restarted.

In this way, when measurement is not performed well, by discarding the data, only accurate data can be used, and stable measurement operation can be performed. Also, There is no need to store measurement data, and the power consumption required for measurement can be reduced. Furthermore, by managing the number of repetitions, even if the propagation time of the ultrasonic wave changes due to a change in temperature, it is possible to measure up to the limit of the number of repetitions regardless of the propagation time.

(Embodiment 17)

FIG. 36 is a flowchart showing the operation of the flow meter according to Embodiment 17 of the present invention. The difference from the first and second embodiments is that a measurement monitoring means 335 is provided for discarding measurement data when the number of repetitions is equal to or less than a predetermined number N2, and the measurement data is discarded when the number of repetitions is equal to or less than a predetermined number. Then, a configuration was provided in which the measurement monitoring means 335 for outputting the start signal again was provided. The configuration is shown in Figure 12.

As shown in Fig. 36, when the number of repetitions in the predetermined measurement performed based on the fluctuation period is less than the predetermined number N2 (for example, 100 times), the measurement data up to that point is discarded. . Then, after waiting for a predetermined time, the measurement was restarted. Thus, even if measurement is performed normally, if the number of repetitions is less than the specified number, it is possible that pressure fluctuations may not be accurately captured, and the data is discarded because it is not a one-cycle measurement. Then, by performing measurement again, a stable measurement operation can be performed. Also, there is no need to store measurement data, and the power consumption required for measurement can be reduced.

(Embodiment 18)

FIG. 37 is a flowchart showing the operation of the flow meter according to Embodiment 18 of the present invention. The difference from the first and second embodiments is that when the number of repetitions is equal to or less than a predetermined number N2, the measurement data is discarded, the start signal is output again, and the synchronization pulse output means 330 as a fluctuation detection means is However, the configuration is provided with the measurement monitoring means 35 that outputs the second output signal when the second cycle is reached and continues the measurement until the end signal in the second cycle. The configuration is shown in Figure 29.

As shown in Fig. 37, when the number of repetitions in the predetermined measurement performed based on the fluctuation cycle is less than the predetermined number N2 (for example, 100 times), the measurement data up to that point is discarded. . After waiting for a predetermined time, the signal of the synchronous pulse output means 330 is output. The second output signal is output when the signal reaches the second cycle, and the measurement that continues the measurement until the end signal of the second cycle is restarted.

Thus, even if measurement is performed normally, if the number of repetitions is less than the specified number, it is possible that pressure fluctuations may not be accurately captured, and the data is discarded because it is not a one-cycle measurement. Then, by performing measurement again, a stable measurement operation can be performed. In addition, when remeasurement is performed, by performing two cycles of measurement, measurement can be performed for a long time and measurement accuracy can be improved.

(Embodiment 19)

FIG. 38 is a flowchart showing the operation of the flow meter according to Embodiment 19 of the present invention. The difference from the first and second embodiments is that, of the pair of transmitting and receiving means, the first number of repetitions N3 at the time of measurement when transmission is performed from one of the transmitting and receiving means and received by the other transmitting and receiving means, and the transmission is performed from the other transmitting and receiving means And the second monitoring number N 4 is compared with the second number of times N 4 at the time of measurement received by one of the transmission / reception means.If the difference between the two number of times is equal to or more than a predetermined number, a start signal is output again. And The configuration is shown in Figure 29.

As shown in FIG. 38, when the difference between the first number of repetitions N3 and the second number of repetitions N4 is equal to or greater than a predetermined number M (for example, 10 times) in a predetermined measurement performed based on the fluctuation cycle, The measurement data up to that point was discarded, and measurement was resumed after waiting for a predetermined time.

Thus, even if the measurement is performed normally, when the difference between the first number of repetitions N 3 and the second number of repetitions N 4 is large, the pressure fluctuation is not accurately captured or the period of the pressure fluctuation fluctuates. Since the measurement has not been performed correctly, a stable measurement operation can be performed by discarding the data and performing the measurement again.

(Embodiment 20)

FIG. 39 is a flowchart showing the operation of the flow meter according to Embodiment 20 of the present invention. The first embodiment differs from the first and second embodiments in that, out of a pair of transmitting and receiving means, the first number of repetitions N 3 at the time of measurement performed by transmitting from one of the transmitting and receiving means and receiving by the other transmitting and receiving means, The second repetition number N 4 at the time of measurement, which is transmitted from the transmission / reception means and received by one of the transmission / reception means, is configured to include the repetition means 3 3 4 for setting the same number. The configuration is shown in Figure 29.

As shown in Fig. 39, by performing the second repetition with the same repetition number as the first repetition number N3 in the predetermined measurement performed based on the fluctuation cycle, even when the pressure fluctuation cycle is severe, By performing the second measurement with the first number of repetitions N 3, the difference from the true value can be measured without a large difference.

Thus, the flow rate can be measured even when the periodic fluctuation of the pressure fluctuation is severe. For example, in the case of a gas meter, there are times when it is necessary to measure the flow rate for security.However, even when the periodic fluctuation of the pressure fluctuation is severe, it is possible to judge whether the flow rate is near the predetermined flow rate by performing such measurement. Can be done.

(Embodiment 21)

FIG. 40 is a flowchart showing the operation of the flow meter according to Embodiment 21 of the present invention. The difference from the first and second embodiments is that the number of times the start signal is output again is up to a predetermined number of times, and a configuration is provided in which a measurement monitoring means 335 for monitoring such that the signal is not repeated forever is provided. The configuration is shown in Figure 29.

As shown in Fig. 40, when the measurement based on the pressure fluctuation fails and the measurement is performed again, the number of re-measurements C is limited (for example, up to two times) so that the processing is infinite. , So that stable flow measurement can be performed.

(Embodiment 22)

FIG. 41 is a block diagram of a flow meter according to Embodiment 22 of the present invention. The difference from Embodiment 12 is that the transmitting and receiving means uses heat propagation as a change in the state of the fluid. 336 is a heat sensor that transmits heat, and 337 is a temperature sensor that receives heat.

Even when a temperature sensor, which is a means for transmitting and receiving heat, is used, the measurement and monitoring means detects each abnormality and performs each process in the same manner as in the embodiment described above, so that the flow rate can be reduced. The measurement can be continuously performed with high accuracy.

(Embodiment 23)

FIG. 42 is a block diagram of a flow meter according to Embodiment 23 of the present invention. In FIG. 42, 415 is an ultrasonic flow rate detecting means for detecting an instantaneous flow rate, 416 is a pulsation determining means for determining whether or not the flow rate value is pulsating, and 417 is a determination of the pulsating determining means. The stable flow rate calculating means for calculating the flow rate value using different means according to the result, and the filter means 418 for digitally filtering the flow rate value.

Next, the operation and action will be described with reference to FIGS. 43 to 45. As shown in FIG. 43, the flow meter of the present invention calculates the difference between the instantaneous flow rate Q (i) measured by the ultrasonic flow rate detecting means and the instantaneous flow rate Q (i-1) measured last time. If the difference is equal to or greater than a predetermined value (for example, 1 liter time), the pulsation determination means determines that there is pulsation. When there is a pulsation, digital filter processing is performed by changing the filter coefficient of the filter processing according to the magnitude of the difference. When there is no pulsation, the instantaneous flow rate value is processed as a stable flow rate without performing the filling process. Here, the digital filter processing is performed according to the flow shown in FIG. 3, and is expressed by the following formula. For example, if the filter coefficient is set, the i-th instantaneous flow rate is Q (i), and the desired stable flow rate after filtering is D (i), D (i) = · Ό (i-1) + (1- )-Q (i). One characteristic of such a filter is that of a low-pass filter, as shown in Fig. 45. As the filter coefficient α is closer to 1 (usually 0.999), only low frequency components are passed. The filter can be used as a filter, and a variable value can be filtered and not passed. When the fluctuation width is small, the filter coefficient is set to α2 (normally α2 = 0.9), and the response to the flow rate fluctuation is improved as a gentle filter characteristic so that it can respond quickly to the flow rate fluctuation. It was made. When the fluctuation width is large, the filter coefficient αΐ (normally 2 = 0.9999) is set, and the fluctuation is suppressed as an extremely low-pass filter characteristic. Further, the pulsation component A (i) can be obtained by A (i) = Q (i) -D (i), and A (i) can be used as a fluctuation range.

As described above, by performing the filtering process when the pulsation is equal to or more than the predetermined value, the fluctuation component can be removed, and the flow rate can be stably measured by one ultrasonic flow rate measuring unit during the pulsation. By performing the filtering process, arithmetic calculations equivalent to the averaging process can be performed without using a large amount of memory for data processing, and the filter characteristic can be freely changed by changing one variable called the filter coefficient α. The filter characteristic can be changed according to the magnitude of the pulsation. Then, at the time of pulsation, steep filter characteristics can be used to stabilize large pulsation, and it is possible to perform filter processing only at the time of pulsation. Then, by performing determination based on the fluctuation range of the pulsation, the filtering process can be changed according to the fluctuation range of the pulsation. By changing the filter characteristics according to the fluctuation range, it is possible to quickly change to a change in the flow rate as a gentle filter characteristic when the fluctuation is small, and to make the filter one characteristic steep when the fluctuation is large. Fluctuations in the flow rate can be greatly suppressed.

Although the present embodiment has been described with reference to FIG. 44 as an example of a digital filtering process, similar effects can be obtained by using other filtering processes.

Although the flow meter is described as a general instrument, use of this flow meter as a gas meter will also allow it to be used in flow piping that generates pulsations, such as piping systems that use gas engine heat pumps. Is possible.

(Embodiment 24)

FIG. 46 is a flowchart showing the operation of the flow meter according to Embodiment 24 of the present invention. The difference from Embodiment 23 is that a pulsation width detection means for detecting a fluctuation width of pulsation from two flow values obtained by performing two filter processes by changing a filter coefficient α is provided. That is. As shown in FIG. 46, as shown in FIG. 46, the first flow rate value subjected to the filtering process using the filter coefficient α ΐ (for example, 1 = 0.999) and the filter coefficient α 2 (for example, α 2 = 0 .9) Compared with the second flow rate value after the filter process was performed, and when the difference became larger than a predetermined value (for example, 1 liter per hour), the filter coefficient α1 with the larger value was gradually reduced. As a result, the flow rate value after the calculation of the stable flow rate was stabilized quickly. However, when 1> Q! 1> α 2> 0.

In other words, if a stable flow rate with a large filter coefficient is used, the response to the flow rate change is delayed when the flow rate changes during pulsation. The flow rate calculated by the flow rate coefficient enables rapid follow-up even if the flow rate changes suddenly during pulsation.

(Embodiment 25)

FIG. 47 is a flowchart showing a flow meter according to Embodiment 25 of the present invention. The difference from Embodiment 23 is that the filter processing is performed only when the flow rate value detected by the instantaneous flow rate detection means is low.

That is, as shown in FIG. 47, when the instantaneous flow rate measured by the ultrasonic flow rate measuring means is less than a predetermined flow rate (for example, 120 liter time), even if pulsation occurs due to the filtering process, The stable flow rate can be measured correctly. In addition, when the flow rate is equal to or more than the predetermined flow rate, the fluctuation range of the flow rate measurement due to the pulsation is small, so that the flow rate measurement can be performed correctly without filtering. Since the flow rate is small, the filter coefficient was set to a large value (for example, hi = 0.999).

As described above, by performing the filter processing only at the low flow rate, it is possible to quickly respond to the flow rate change at the large flow rate and to significantly suppress the influence of the pulsation at the low flow rate.

(Embodiment 26)

FIG. 48 is a flowchart showing the operation of the flow meter according to Embodiment 26 of the present invention. The difference from the embodiment 23 is that the filter processing means is configured to change one filter characteristic according to the flow rate value.

That is, as shown in FIG. 48, when the instantaneous flow rate measured by the ultrasonic flow rate measuring means is equal to or larger than a predetermined value (eg, 120 liter Z time), the fill coefficient α 1 (eg, α 1 = 0) 9) And, when the flow rate is less than the predetermined value, the filter coefficient is set to 2 (for example, α 2 = 0.999). Therefore, when the flow rate is low, the filter coefficient H2 is increased to focus on the measurement of the stable flow rate. For example, when using a gas meter, leak detection, appliance discrimination, and pilot fire registration are performed accurately. In addition, when the flow rate is large, the fill factor coefficient α1 is reduced to respond quickly to the change in flow rate, thereby improving the responsiveness of the integrated flow rate.

In this way, by changing the filter characteristics according to the flow rate value, filter processing is performed at low flow rates to quickly respond to flow rate changes at high flow rates and greatly reduce the effects of pulsation at low flow rates be able to. When the flow rate is high, the responsiveness is increased, and when the flow rate is low, the pulsation can be suppressed.

(Embodiment 27)

FIG. 49 is a flowchart showing the operation of the flow meter according to Embodiment 27 of the present invention. The difference from the twenty-third embodiment is that the filter processing means is configured to change the filter characteristics depending on the flow time interval of the ultrasonic flow rate detection means.

That is, as shown in FIG. 49, when the time interval for measuring the flow rate by the ultrasonic flow rate measuring means is long (for example, 12 seconds), the filter coefficient α1 is a small value (for example, 1 = 0. 9) was used, and when the time interval was short, filtering was performed using a large value of the filter coefficient α2 (for example, 1 = 0.999). As described above, by changing the filter characteristics according to the interval of the flow rate detection time, the fluctuation can be suppressed by a gentle filter characteristic when the measurement interval is short, and by a steep filter characteristic when the measurement interval is wide.

(Embodiment 28) FIG. 50 is a flowchart showing the operation of the flow meter according to Embodiment 28 of the present invention. <A difference from Embodiment 23 is that the fluctuation Φ; of the flow rate value calculated by the stable flow rate calculating means is within a predetermined value. The filter characteristic is changed so that

That is, as shown in FIG. 50, when the fluctuation value of the flow rate obtained by the stable flow rate calculation processing after the filter processing is equal to or more than a predetermined value (for example, 1 liter Z hour), the filter coefficient α is set. Control is performed in a direction to increase the flow rate fluctuation, and when it is less than the predetermined value, the filter coefficient α is reduced to perform the filter processing in a state that can respond to the flow rate change.

As described above, the flow rate fluctuation can be constantly suppressed to a predetermined value or less by adaptively changing the filter characteristic so that the fluctuation value after the stable flow rate calculating means is within the predetermined value.

The amount of increase in the filter coefficient is changed depending on the fluctuation value of the flow rate.When the fluctuation amount is large, the increase amount is increased, and when the fluctuation amount is small, the increase amount is reduced and the filter coefficient is changed. By doing so, fluctuations in the flow rate can be suppressed promptly.

(Embodiment 29)

FIG. 51 is a block diagram of a flow meter according to Embodiment 29 of the present invention. The difference from the embodiment 23 is that the instantaneous flow rate detecting means is a thermal flow rate detecting means 4 19. As shown in FIG. 51, the measurement flow rate fluctuates when the pressure fluctuates by using the thermal flow rate detection means 4 19, but the method of Embodiments 23 to 28 is used. Thus, the same effect can be obtained, and the flow rate can be measured stably and accurately.

(Embodiment 30)

FIG. 52 is a block diagram of a flow meter showing the embodiment 30 of the present invention.

A flow rate measuring section 500 through which the fluid to be measured flows; a pair of ultrasonic transducers 501 and 502 provided in the flow rate measuring section 500 to transmit and receive ultrasonic waves; and one ultrasonic transducer 5 A drive circuit 5 0 3 for driving 0 2 and an ultrasonic wave connected to the other ultrasonic transducer 5 0 1 A reception detection circuit 504 for detecting the signal, a timer 505 for measuring the propagation time of the ultrasonic signal, a control unit 507 for controlling the drive circuit 503, and a flow rate calculated from the output of the timer An arithmetic unit 506 to be obtained and a periodicity changing means 508 for sequentially changing the driving method of the drive circuit 503 are provided. The difference from the conventional example is that a periodicity changing means 509 is provided, and a detailed diagram of the periodicity changing means 508 is shown in FIG. The reference numeral 5100 generates a first oscillator, here an oscillation signal of 500 kHz. Reference numeral 511 denotes a second oscillator, which generates an oscillation signal of 500 kHz. Numeral 512 denotes a switch, which outputs the output of the first oscillator 510 or the output of the second oscillator 511 to the switching drive circuit 503 by the output of the controller 507.

First, the control unit 507 outputs a switching signal to the switching unit 512 to select the first oscillator 510. Next, the time measurement of the timer 505 is started, and at the same time, a transmission start signal is output to the drive circuit 503. The drive circuit 503 that has received the transmission start signal drives the ultrasonic vibrator 502 with an oscillation signal of 500 kHz, which is an input from the switch 5 12. Subsequent operations are the same as in the conventional example. Next, the control unit 507 outputs a switching signal to the switch 511 and selects the second oscillator 511. Then, as in the previous flow measurement, the time measurement of the timer 505 is started, and at the same time, a transmission start signal is output to the drive circuit 503. The drive circuit 503 that has received the transmission start signal drives the ultrasonic transducer 501 with an oscillation signal of 520 kHz, which is an input from the switch 5 12.

Thereafter, this operation is alternately continued to measure the flow rate. Figure 54 shows the reception detection timing for such a measurement. As shown in this figure, the reception signals at 500 kHz and 500 kHz are shifted in time, and the reception detection timings are as shown in (A) and (B) in Fig. 54. Shift in time. Therefore, in this embodiment, the control unit controls the periodicity changing means so as to sequentially change the cycle in the flow rate measurement so that the measurement cycle is not constant. Since the synchronized noise does not always exist in the same phase at the time of reception and is dispersed, the measurement error can be reduced. In addition, the periodicity changing means is configured to switch and output a plurality of frequency output signals, and the control unit controls the frequency setting of the periodicity changing means to change the driving frequency of the driving circuit every measurement, so that the driving frequency is changed. By changing this, the reception detection timing can be changed over time corresponding to the period fluctuation of the drive signal, so that noise synchronized with the measurement period or the transmission period of ultrasonic waves does not always exist in the same phase at the time of reception. Therefore, the measurement error can be reduced.

In Embodiment 30, the drive frequency is changed by switching between two oscillators, but the same effect can be obtained if the drive frequency can be changed to drive the ultrasonic transducer. It is not limited to the number of oscillators, drive frequency, and switch configuration.

(Embodiment 3 1)

FIG. 55 is a block diagram of a flow meter showing the embodiment 31 of the present invention.

A flow rate measuring section 500 through which the fluid to be measured flows, a pair of ultrasonic transducers 501 and 502 provided in the flow rate measuring section 500 to transmit and receive ultrasonic waves, and one of the ultrasonic transducers The drive circuit 503 for driving, the reception detection circuit 504 connected to the other ultrasonic transducer to detect an ultrasonic signal, and the output of the reception detection circuit 504 to drive the ultrasonic transducer again A control unit 507 that controls the drive circuit 503 a predetermined number of times, a timer 505 that measures a predetermined number of elapsed times, and a calculation unit 5 that calculates the flow rate from the output of the timer 505 And a periodicity changing means 508 for sequentially changing the driving method of the driving circuit 503.

FIG. 56 is a detailed block diagram of the periodicity changing means.

5 1 2 is a first delay, which generates an output signal 150 s after receiving an input signal from the control unit 5 07, 5 1 3 is a second delay, which is the control unit 5 0 7 An output signal is generated 150.5 s after receiving these input signals, and 514 is a third delay which is 15 1 μs after receiving an input signal from the control unit 507. Later, the output signal is generated. 5 15 is the fourth delay, which is the input signal from the control unit 5 07 After receiving 151.5 s, an output signal is generated. 5 15 is a switch which selects the first to fourth delay outputs according to the output of the control unit 507 and drives the drive circuit 5. 0 Output to 3.

The difference from the first embodiment is that the control unit 507 receives the output of the reception detection circuit 504 and drives the ultrasonic vibrator again, and this operation is repeated as an integral multiple of the delay setting number of 4. During the repetition, the delay time of the periodicity changing means 508 is sequentially switched every time an ultrasonic wave is received.

With this configuration, the control unit 507 changes the delay setting each time the ultrasonic wave is detected, so that the influence of the reverberation of the ultrasonic wave transmitted immediately before during one measurement or the tailing of the ultrasonic transducer is reduced. Dispersion and averaging can be performed, and measurement errors can be reduced.

In addition, the width of the cycle changed by the cycle changing means is a value obtained by equally dividing 2 s, which is the position cycle of the resonance frequency of 500 kHz of the ultrasonic vibrator, so that the sum of all the settings and the average value are: However, it is possible to minimize the error generated by the reverberation or tailing of the ultrasonic sensor, which is noise having a period of 2 s.

Furthermore, since the number of times the measurement is repeated is an integral multiple of 4 which is the number of changes of the periodicity changing means, the same number of measurements at each constant value of the periodicity changing means must be performed in one flow measurement. And the measurement results are not biased, so that the measurement results can be stabilized.

Furthermore, the order of the pattern for changing the periodicity is the same for the measurement in the upstream direction and the measurement in the downstream direction. Specifically, in the measurement from upstream to downstream, the first delay, then the second delay, then the third delay, then the fourth delay, and then back to the first delay repeat. In the measurement from downstream to upstream, the delay is always selected in the same order. By doing so, the flow rate measurement in the upstream direction and the downstream direction always becomes the same condition, and the measurement result can be stabilized particularly when there is a flow rate fluctuation. Although the delay time is changed by switching the four delays in Embodiment 31, the same effect can be obtained if the drive timing can be changed to drive the ultrasonic transducer. It is not limited by the time, the number of delays, or the configuration of the switch.

Although the delay time to be changed is inserted between the control unit 507 and the drive circuit 503, the same effect can be obtained even between the reception detection circuit 504 and the control unit 507. be able to.

Also, the delay change width is 2 s, the number of settings to be changed is 4 and the change for each adjacent setting is 0.5 // 4 divided by 2 // s, but a value that is an integral multiple of one cycle The value is not limited to this value as long as it is a value divided at equal intervals.

(Embodiment 32)

FIG. 57A is a block diagram of the periodicity changing means of the flow meter according to the embodiment 32. 5 18 is an oscillator, and 5 19 is a phase converter. The oscillator outputs a signal at a frequency of 500 kHz, and the phase converter advances or delays the phase of the oscillator signal in accordance with the phase conversion signal from the control unit 507 and outputs the signal. For example, when the phase control signal is Hi, the output of the oscillator 518 is output as it is, and when the phase control signal is Lo, the output signal of the oscillator 518 is advanced by 180 ° and output. Figure 57B shows the reception signal and reception detection timing at this time.

As shown in this figure, since the receiving point is shifted by 12 periods, the shift time is I S.

As described above, the reception detection timing can be changed by converting the phase fluctuation of the drive signal into time by changing the drive phase. For this reason, noise synchronized with the measurement cycle or the transmission cycle of the ultrasonic wave does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

In Embodiment 32, the phase of the drive signal is changed by switching the two phases. However, it is possible to drive the ultrasonic transducer by changing the drive phase. The same effect can be obtained if possible, and it is not limited to the phase to be changed and the configuration of the switch.

(Embodiment 33)

FIG. 58 is a block diagram of a periodicity changing means of the flow meter according to the thirty-third embodiment. Reference numeral 520 denotes a first oscillator, which outputs an oscillation signal having a resonance frequency of 500 kHz of the ultrasonic vibrator. Reference numeral 521 denotes a second oscillator, which outputs an oscillation signal of 200 kHz. Reference numeral 522 denotes an ONZOFF circuit which switches whether to output the output of the second oscillator to the waveform adding unit 523 according to the ONZO F F switching signal of the control unit 507. Waveform adder 523 combines the input waveforms and outputs the result to drive circuit 503.

Ultrasonic transducers can receive ultrasonic signals with large amplitude when driven at about 500 kHz, and can hardly receive ultrasonic signals when driven with only 200 kHz signal components. However, by adding or not adding an oscillation signal of about 200 kHz to an oscillation frequency of about 500 kHz, the period of the received ultrasonic signal changes slightly. As a result, the reception detection timing can be changed. For this reason, noise synchronized with the measurement cycle or the transmission cycle of ultrasonic waves does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

(Embodiment 34)

FIG. 59 is a block diagram of a periodicity changing means of the flow meter according to the thirty-fourth embodiment. Reference numeral 520 denotes a first oscillator, which outputs an oscillation signal having a resonance frequency of 500 kHz of the ultrasonic vibrator. 52 1 is a second oscillator, which outputs an oscillation signal of 200 kHz. Reference numeral 524 denotes a phase conversion unit that converts the phase of the output signal of the second oscillator 521 by 180 ° according to the output of the control unit 507 and outputs the converted signal. Reference numeral 523 denotes a waveform addition unit that combines the input waveforms and outputs the synthesized waveform to the drive circuit 503.

An ultrasonic transducer can receive an ultrasonic signal with a large amplitude when driven at about 500 kHz, and can hardly receive an ultrasonic signal when driven only with a signal component of 200 kHz. However, for an oscillation frequency of about 500 kHz, the phase of the oscillation signal of about 200 kHz The period of the ultrasonic signal received by driving based on the added signal obtained by inverting the signal by 180 ° for each measurement changes slightly. As a result, the reception detection timing can be changed. For this reason, noise synchronized with the measurement cycle or the transmission cycle of the ultrasonic wave does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

(Embodiment 35)

FIG. 60 is a block diagram of the periodicity changing means of the flow meter according to the thirty-fifth embodiment. Reference numeral 525 denotes a first oscillator, which outputs an oscillation signal having a resonance frequency of the ultrasonic transducer of 500 kHz. Reference numeral 526 denotes a second oscillator, which outputs an oscillation signal of 200 kHz. Reference numeral 522 converts the frequency of the signal input to the frequency conversion unit and outputs the converted signal. Here, it is converted to 100 kHz of 1Z2. Reference numeral 523 denotes a waveform adding unit that combines the input waveform and outputs the synthesized waveform to the driving circuit 503.

Ultrasonic transducers can receive ultrasonic signals with large amplitude when driven at about 500 kHz, and can hardly receive ultrasonic signals when driven with only 200 kHz or 100 kHz signal components. However, the period of the ultrasonic signal received by driving based on the addition signal obtained by adding about 200 kHz to the oscillation frequency of about 500 kHz and the addition signal obtained by adding 100 kHz to the oscillation frequency of 500 kHz is Subtle changes. As a result, the reception detection timing can be changed. For this reason, noise synchronized with the measurement period or the transmission period of the ultrasonic wave does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

(Embodiment 36)

FIG. 61 is a block diagram of a flow meter according to the thirty-sixth embodiment.

A flow measuring unit 500 through which the fluid to be measured flows, a pair of ultrasonic transducers 501 and 502 provided in the flow measuring unit for transmitting and receiving ultrasonic waves, a driving circuit 503 for driving one ultrasonic transducer 502, and the other Detection circuit 504 that is connected to the ultrasonic transducer 501 of the first embodiment and detects an ultrasonic signal, and a first receiver that measures the propagation time of the ultrasonic signal 5 2 7, a second timer 5 2 8 for measuring the time from when the reception detection circuit 5 4 4 detects the reception until the value of the first timer 5 2 7 changes, and a driving circuit 5 0 A control unit 530 for controlling the control unit 3; an operation unit 506 for calculating the flow rate from the outputs of the first and second imagers 527 and 528; and an ultrasonic transducer 510 , 502, the drive circuit 503, the reception detection circuit 504, a switching circuit 509 for switching the connection, and the temperature sensor that measures the temperature of the flow meter and outputs it to the control unit 530 And a voltage sensor 532 for measuring the voltage of the power supply operating the flowmeter.

Then, the control unit 530 outputs a measurement start signal to the drive circuit 503, and at the same time, starts the time measurement of the first evening timer 527. When there is a signal input, the drive circuit 503 drives the ultrasonic vibrator 502 to transmit ultrasonic waves. The transmitted ultrasonic wave propagates through the fluid and is received by the ultrasonic transducer 501. The reception detection circuit 504 outputs the received ultrasonic signal to the first receiver 527 and the second receiver 528. The first timer 527 receives an input signal from the reception detection circuit 504 and stops time measurement. The second evening timer 528 receives the output of the reception detection circuit 504 and starts timing, and stops the timing in synchronization with the count-up timing output from the first evening timer 527. The calculation unit 506 receives the time measurement results of the first timer 527 and the second timer 528, and obtains the flow rate by calculation.

Figure 62 shows the operation timing of the first timer 527 and the second timer 528. As shown in FIG. 62, the state of the first timer 527 changes at the rising edge of the clock, so the portion indicated by A is measured extra. Since the measurement resolution of the first timer 527 is at the interval shown by B in FIG. 62, the portion A which is a measurement error occurs for each measurement. Therefore, the extra part A is measured by the second timer 528 and subtracted by the arithmetic part 506, and the propagation time of the ultrasonic wave with higher resolution is obtained to obtain an accurate flow rate value. The control unit 530 starts the first evening timer 527 and simultaneously outputs a start signal to the second timer 528 to start the second evening timer 528. When it is time to count up the first timer 527, the first timer 527 Then, an output signal synchronized with the count-up timing is output to the second timer 528, and the second timer 528 is stopped. The value of the timer 528 at this time is the time measured at the time of one clock of the first evening. This time is processed by the arithmetic section 506, and the time per clock of the second evening image 528 is obtained, and the time per clock of the second evening image 528 used for the calculation is corrected.

This operation is performed when the output of the temperature sensor 531 or the output of the power supply voltage sensor 532 changes more than the set value. By doing so, the stability of the temperature and the power supply voltage is not required for the heater 528, and inexpensive components can be used. In addition, power consumption can be reduced without the need for frequent corrections.

Then, since the flow rate is calculated by subtracting the value of the second timer 528 from the value of the first timer 527, the timing resolution is equivalent to that of the second timer 528 . Since the operation time of the second timer 528 is very short, power consumption can be reduced, and a flowmeter with high resolution can be realized with low power consumption. Furthermore, accurate flow measurement can be performed if the second timer 528 operates stably until flow measurement after correction, so accurate measurement can be performed even if the second timer 528 does not have long-term stability. It can be performed. A high-precision flowmeter can be easily realized with general parts.

Also, a temperature sensor 531 is provided, and when the output of the temperature sensor 531 changes by more than a set value, the second timer 528 is corrected by the first timer 527. For this reason, even if the second timer 528 changes its characteristic with respect to a temperature change, it can be corrected and accurate measurement each time a temperature change occurs. Since correction is performed only when necessary, power consumption can be reduced.

Further, a voltage sensor 532 is provided, and when the output of the voltage sensor 532 changes by more than a set value, the second evening time 528 is corrected by the first evening time 527. Therefore, even if the second timer 528 changes its characteristic with respect to the power supply voltage change, it can be corrected and accurate measurement each time the power supply voltage change occurs. And when needed Since only correction is performed, power consumption can be reduced.

In order to perform such correction, a crystal oscillator is used for the clock of the first timer 527 and a CR oscillation circuit is used for the clock of the second timer 528. It is very stable with a clock using a crystal oscillator, but it takes time from the start of operation to the stable operation. In addition, although the CR oscillation circuit cannot secure long-term stability, it can easily realize a stable operation that operates quickly and operates quickly and asynchronously. By using a crystal oscillator for the clock of the first timer 527 and a CR oscillation circuit for the clock of the second timer 528, a stable timer with high resolution can be easily realized.

In FIG. 62 of Embodiment 36, the timing at which the second timer stops is set to the timing at which the clock of the first timer falls after the second evening timer operates. As long as the timing is synchronized with the evening of 1, an accurate time can be obtained by the subsequent calculation, so that the timing is not limited to this evening.

(Embodiment 37)

FIG. 63 is a block diagram of the flow meter according to the third embodiment.

Also, a flow rate measuring section 500, a pair of ultrasonic transducers 501, 502 provided in the flow rate measuring section 500 for transmitting and receiving ultrasonic waves, and one ultrasonic transducer 502, The drive circuit 503 to be driven, the reception detection circuit 504 connected to the other ultrasonic transducer 501 to detect the ultrasonic reception signal, and the ultrasonic vibration again after receiving the output of the reception detection circuit 504 The controller 507 controls the drive circuit 503 a predetermined number of times to drive the child 502, the timer 505 measures the elapsed time of the predetermined number of times, and calculates the flow rate from the output of the timer 505. And a delay section 533 as periodicity stabilizing means for sequentially changing the driving method of the drive circuit 503.

Then, the control unit 507 outputs a measurement start signal to the delay unit 533, and at the same time, starts the time measurement of the timer 505. The delay section 5 3 3 is set from the control section. After a delay time set by the constant signal, a signal is output to the drive circuit 503. When there is a signal input, the drive circuit 503 drives the ultrasonic vibrator 502 to emit ultrasonic waves. The transmitted ultrasonic wave propagates through the fluid and is received by the ultrasonic transducer 501. The reception detection circuit 504 outputs the received ultrasonic signal to the delay unit 533, and operates the drive circuit in the same manner as before to transmit the ultrasonic wave again. The control unit 507 that has received the output signal of the reception detection circuit 504 counts this repetitive operation, and stops the timer 505 when a predetermined number of times is reached. The calculation unit 506 receives the time measurement result of the timer 505 and calculates the flow rate by calculation.

The control unit 507 receives the value of the timer 505, and sets the delay time of the delay unit 533 so that it is always constant. By doing so, the control unit 507 controls so that the measurement cycle is always constant. With this configuration, the measurement period is always constant even when the propagation time changes, so that noise synchronized with the measurement period or the transmission period of the ultrasonic wave is always present during reception regardless of the propagation time fluctuation. Since the phases are the same, the measurement error can be kept constant, and the flow measurement can be stabilized even with a very long noise period.

In addition, since the control unit 507 controls the delay unit 533 so as to keep the measurement time constant, the measurement cycle can be made constant by simple calculation without calculating the propagation time of each ultrasonic wave. Can be controlled.

In Embodiment 37, the measurement period was made constant by changing the delay time. However, the same effect can be obtained if the measurement period becomes constant, such as changing the distance between the ultrasonic transducers. The same effect can be obtained by adopting the method described above.

If there is a flow, the propagation time of the ultrasonic wave from the upstream to the downstream is different from the propagation time of the ultrasonic wave from the downstream to the upstream.Therefore, different delays should be set to stabilize the measurement cycle. Is also possible.

When the flow rate is larger and the error due to the periodic noise can be ignored, the operation of the periodic stabilization means is stopped, and the power can be reduced. In addition, at the start of measurement, the flow rate is measured while changing the setting of the measurement cycle stabilization means, and the measurement cycle at which the measurement result does not change the most during the measurement cycle fluctuation is set as the target measurement cycle, so that more stable measurement The result can be obtained. Industrial applicability

As described above, according to the flowmeter of the present invention, the following effects can be obtained.

In order to solve the above problems, the present invention provides a transmitting / receiving means provided in a flow path for transmitting and receiving using a change in the state of a fluid, a repeating means for repeating the transmission and reception, and a propagation time repeated by the repeating means. Since there are provided a time measuring means for measuring, a flow detecting means for detecting a flow rate based on the value of the time measuring means, and a number changing means for changing to a predetermined number of repetitions, the flow is changed by changing to an optimum number of repetitions. The effect of fluctuations in flow can be suppressed, and stable flow measurement can be realized with high accuracy.

In addition, since a pair of transmitting and receiving means using sound wave propagation is provided as a change in the state of the fluid, the use of the sound wave transmitting and receiving means enables the propagation of the sound wave even when the state of the fluid changes. The flow rate can be measured accurately and stably by changing to the optimum number of repetitions for fluctuation.

In addition, since a transmission / reception unit that uses heat propagation as a change in the fluid state is provided, the use of the heat transmission / reception unit allows heat to be transmitted even when the fluid state changes. By changing the number of repetitions to the optimal number, the flow rate can be measured accurately and stably.

Further, an elapsed time detecting means for detecting information on the way of the propagation time repeatedly measured by the repeating means, a cycle detecting means for detecting a cycle of the flow rate variation from the information of the elapsed time detecting means, It has a number change means to set the measurement time to an almost integral multiple of the measured cycle, so no specific detection means is required, and the cycle is detected from the intermediate information of the time measurement means before detecting the flow rate. Since it can be an integral multiple of the cycle, the flow rate measurement can be performed stably and accurately. Also, a data holding unit that holds at least 1 偭 or more of each propagation time of repetitive transmission and reception obtained by the elapsed time detection unit, and compares the data held by the data holding unit with the measured propagation time data. Therefore, the period detecting means for detecting the period can be provided. Therefore, the period can be detected by holding and comparing the instantaneous time measurement information by the data holding means.

In addition, since the number-of-times changing means is configured to operate at the time of predetermined processing, by performing the processing only at the time of predetermined processing, it is possible to minimize the processing required and to significantly reduce power consumption. it can.

In addition, since the number-of-times changing means is configured to operate each time a predetermined flow rate is measured, it is possible to measure the flow rate stably and accurately even in a flow that fluctuates drastically by performing the measurement every time the predetermined flow rate is measured.

In addition, since the number-of-times changing means is configured to be performed before the flow rate measurement process, the number of repetitions is set to a predetermined number before the flow rate measurement is performed, so that the flow rate measurement can be performed stably and accurately.

In addition, since the predetermined processing is configured to perform abnormality determination means for determining an abnormality in the flow rate from the measured flow rate and flow rate management means for managing the usage state of the flow rate from the measured flow rate, the processing for the abnormality determination and the flow rate management is performed. By setting only the number of times, the process of changing the number of times can be minimized and the power consumption can be reduced.

Also, since the number of repetitions that match the cycle obtained by the cycle detection means is used for the next flow rate measurement, it is used for the next measurement, so that repeated measurement for cycle detection is not required. Thus, power consumption can be reduced.

Further, since the number-of-times changing means is operated when the measured flow rate is less than the predetermined flow rate, it is possible to reduce the power consumption without processing when the flow rate is high, by performing the operation only when the flow rate is less than the predetermined flow rate.

A transmitting / receiving unit provided in the flow path for transmitting / receiving a change in the state of the fluid; a timing unit for measuring a propagation time transmitted / received by the transmitting / receiving unit; Flow detecting means for detecting a flow rate, a fluctuation detecting means for measuring a fluctuation in the flow path by the transmitting and receiving means, and a measuring control means for starting measurement in synchronization with a fluctuation timing of the fluctuation detecting means. By measuring the fluctuations in the flow path with the transmission / reception means, there is no need to provide a separate sensor for detecting fluctuations, making it possible to reduce the size, simplify the flow path, etc., and if fluctuations occur However, the flow rate can be measured stably and accurately in a short time.

In addition, since a pair of transmitting and receiving means that uses sound wave propagation as a fluid state change is provided, the fluid state change can be detected by the sound wave transmitting and receiving means, and measurement is started in synchronization with the fluctuation timing. By doing so, the flow rate can be measured accurately and stably.

In addition, since the transmitter / receiver uses heat propagation as a change in the fluid state, the change in the state of the fluid can be detected by the heat transmitter / receiver, and measurement can be started in synchronization with the timing of the fluctuation. The flow rate can be measured accurately and stably. A first vibrating means and a second vibrating means provided in the flow path for transmitting and receiving a sound wave; a switching means for switching the transmitting and receiving operations of the first vibrating means and the second vibrating means; A fluctuation detecting means for detecting a pressure fluctuation in the flow path of at least one of the second vibrating means; a time measuring means for measuring a propagation time of a sound wave transmitted and received by the first vibrating means and the second vibrating means; When the output of the means changes by a predetermined amount, the time measuring means measures a first time T1 which propagates from the first vibrating means on the upstream side of the flow path to the second vibrating means on the downstream side. When the output changes in reverse to the predetermined change, the time measurement means controls the second time measurement T2 to be transmitted from the second vibration means on the downstream side of the flow path to the first vibration means on the upstream side. Control means, and the first clock time T 1 Since the system is equipped with a flow rate detecting means that calculates the flow rate using the second clocking time T2, the phase of the pressure fluctuation and the timing of the measurement are measured by measuring at the timing when the change of the pressure fluctuation is reversed. Can be shifted, and measurement errors due to pressure fluctuations can be offset. In addition, the measurement of the first clocking time T1 is started when the output of the fluctuation detecting means changes by a predetermined amount, and the measurement of the second clocking time T2 is started when the output of the fluctuation detecting means changes in a direction opposite to the predetermined change. Measurement control, and at the next measurement, when the output of the fluctuation detecting means changes in reverse to the predetermined change, measurement of the first time T1 is started, and when the output of the fluctuation detecting means changes by a predetermined amount. Start the measurement of the second clock time T2 The measurement control means that performs the measurement control and the second clock time T2 obtained by using the previous first clock time T1 and the second clock time T2 while alternately changing the measurement start (1) Flow rate and the flow rate detection means for calculating the flow rate by successively averaging the second flow rate obtained using the first time measurement time T1 and the second time measurement time T2 for the next measurement. Change the timing as described above, the first time T1 and the second time T2 By doing so, even if the pressure fluctuation is asymmetric on the high and low pressure sides, the effect of the pressure fluctuation can be offset.

In addition, since the configuration is provided with a repetition means for performing transmission and reception a plurality of times, averaging can be performed by increasing the number of times of measurement, and stable flow rate measurement can be performed. In addition, since there is provided a repetition unit that performs transmission and reception multiple times over an integral multiple of the fluctuation period, pressure fluctuations are averaged by measuring at the fluctuation period, and a stable flow rate can be measured.

Further, since the transmission / reception measurement is started when the output of the fluctuation detection means changes by a predetermined amount, and the repetition means performs the transmission / reception measurement of the sound wave repeatedly until the output of the fluctuation detection means changes the same as the predetermined change, Since the start and stop of the measurement can be made to coincide with the cycle of the pressure fluctuation, the measurement can be performed at the fluctuation cycle, and the pressure fluctuation can be averaged and a stable flow rate can be measured.

Further, since the first vibration means and the second vibration means are provided with a selection means for switching between a case where the first vibration means is used for transmitting and receiving a sound wave and a case where the first vibration means is used for detecting a pressure fluctuation, the first vibration means and the second vibration means are provided. At least one of them can be used for pressure detection, and both flow measurement and pressure measurement can be achieved.

In addition, a fluctuation detecting means for detecting the vicinity of zero of the AC component of the fluctuation waveform is provided. By detecting the fluctuation near the zero component of the fluctuation, the range of the flow measurement time can be started from around the fluctuation zero, and the flow fluctuation can be measured by measuring the flow within the time where the fluctuation is small. Time measurement can be stabilized.

In addition, a cycle detecting means for detecting a cycle of a signal of the fluctuation detecting means, and a measurement control means for starting a measurement only when the cycle detected by the cycle detecting means is a predetermined cycle is provided. By starting the measurement only at the time, measurement can be performed at a predetermined fluctuation, and a stable flow rate can be measured.

In addition, when a signal from the fluctuation detecting means cannot be detected, a detection canceling means that automatically starts measurement after a predetermined time is provided. Can be measured.

In addition, since the transmitting / receiving means, the first vibrating means, and the second vibrating means are composed of piezoelectric vibrators, the use of the piezoelectric vibrator allows ultrasonic waves to be used for transmission / reception and also detects pressure fluctuations. can do.

A transmission / reception unit provided in the flow path for transmitting / receiving using a change in the state of the fluid; a repetition unit for repeating the signal propagation of the transmission / reception unit; and measuring a propagation time during the repetition by the repetition unit. Time measuring means, flow rate detecting means for detecting a flow rate based on the value of the time measuring means, fluctuation detecting means for detecting fluid fluctuation in the flow path, measurement control means for controlling each of the means, and each of the means Since there is a measurement and monitoring means for monitoring abnormalities in the flow path, if there is a fluctuation in the flow in the flow path, the flow rate can be measured in accordance with the fluctuation and the abnormality can be quickly detected by the measurement and monitoring means. Corrective measures can be taken in the event of an abnormality, the measured value is stable, the flow rate can be measured accurately, and reliability can be improved.

In addition, since a pair of transmitting and receiving means using the propagation of sound waves as a change in the state of the fluid is provided, the flow rate can be measured even if the fluid fluctuates by using the sound waves, and the measurement and monitoring means can be used to handle abnormalities. Can be performed accurately and reliability can be improved. In addition, since it has transmission and reception means using the propagation of heat as a state change of the fluid, By using heat propagation, the flow rate can be measured even if the fluid fluctuates, and the measurement and monitoring means can take corrective measures when an abnormality occurs, thereby improving reliability.

A pair of transmitting / receiving means provided in the flow path for transmitting / receiving a sound wave; a repeating means for repeating signal propagation of the transmitting / receiving means; and measuring a propagation time of the sound wave during the repetition by the repeating means. Time measuring means, flow rate detecting means for detecting a flow rate based on the value of the time measuring means, fluctuation detecting means for detecting fluid fluctuation in the flow path, measurement control means for controlling each of the means, and the measurement control After the instruction signal of the means, a start signal instructing the start of sound wave transmission at the time of the first output signal of the fluctuation detecting means, and an end signal instructing the repetition of transmission and reception of sound waves at the time of the second output signal of the fluctuation detecting means. And measurement and monitoring means for monitoring abnormalities of the start signal and the end signal, so that when there is a change in the flow in the flow path, the flow is measured in synchronization with the fluctuation cycle and the measurement and monitoring means is used. Detect abnormalities It is possible to, the measurement value can be measured stably and accurately the flow rate, or One abnormal response to be accurately line, it is possible to improve the reliability of the measurement flow rate value. In addition, when the start signal is not generated within a predetermined time after the instruction of the measurement control means, the measurement monitoring means for instructing the start of the transmission of the sound wave after a predetermined time is provided. Even when there is no signal, the flow rate can be measured at predetermined time intervals, and loss of data can be prevented.

In addition, when the start signal is not generated within a predetermined time after the instruction of the measurement control means, the measurement monitoring means for instructing the start of the transmission of the sound wave after a predetermined time and performing the measurement at a predetermined number of repetitions is provided. Even if there is no fluctuation and there is no start signal within a predetermined time, the flow rate can be measured at a predetermined number of repetitions every predetermined time and data loss can be prevented.

In addition, when the start signal is not generated within a predetermined time after the instruction from the measurement control unit, the measurement monitoring unit that does not perform measurement until the instruction from the next measurement control unit is provided, so it waits for the next measurement instruction. By doing so, unnecessary measurement can be stopped and power consumption can be reduced. In addition, if there is no end signal within a predetermined time after the start signal, there is a measurement monitoring means to end the reception of the sound wave, so that the measurement is stopped waiting for the end by forcibly terminating And the next processing can be performed, and stable measurement operation can be performed.

In addition, when the end signal is not generated within a predetermined time after the start signal, the reception of the sound wave is terminated, and the measurement monitoring means for outputting the start signal again is provided. The measurement does not stop waiting for completion, and the measurement is performed again by outputting the start signal again, and stable measurement operation can be performed.

In addition, when the number of repetitions becomes abnormal, there is a measurement monitoring unit that stops transmission / reception processing, so when the number of repetitions is abnormal, the measurement is stopped to use only accurate data and flow Measurement can be performed.

Also, of the pair of transmission / reception means, the first number of repetitions at the time of measurement transmitted from one transmission / reception means and received by the other transmission / reception means, and transmitted from the other transmission / reception means and received by one transmission / reception means Compare the second number of repetitions at the time of measurement, and when the difference between the two repetitions is equal to or greater than a predetermined number, a measurement monitoring unit that outputs a start signal again is provided. Therefore, accurate measurement of flow rate can be performed by measuring in a state where the fluctuation cycle is stable.

Also, of the pair of transmission / reception means, the first number of repetitions at the time of measurement transmitted from one transmission / reception means and received by the other transmission / reception means, and transmitted from the other transmission / reception means and received by one transmission / reception means Since there is a repetition means that sets the second number of repetitions during measurement to be the same, the same number of repetitions allows the specified flow rate measurement to be performed even when the fluctuation cycle is unstable. it can.

Also, the number of times the start signal is output again is up to the specified number of times, and measurement monitoring means is provided so as to monitor it so that it will not be repeated forever, so processing is continued indefinitely by limiting the number of times of re-measurement And stable flow measurement can be performed. In addition, the flow rate can be calculated from the reciprocal difference Since ultrasonic waves are used, transmission and reception can be performed without being affected by the fluctuation frequency in the flow path, and the flow rate is measured from the reciprocal difference of the time when the propagation time is measured by repeating transmission and reception. By doing so, even long-period fluctuations can be measured in one-period units, and the difference in propagation time due to fluctuations can be offset by the reciprocal difference.

Further, an instantaneous flow rate detecting means for detecting an instantaneous flow rate, a pulsation determining means for determining whether or not the flow rate value is pulsating, and at least one of calculating a flow rate value using means different depending on the determination result of the pulsation determining means. Since more than one stable flow rate calculating means is provided, it is possible to calculate the stable flow rate with one flow rate measuring means according to the fluctuation amount by determining the fluctuation of the measured flow rate and switching the flow rate calculating means. can do.

In addition, since there are provided an instantaneous flow rate detecting means for detecting an instantaneous flow rate, a filter processing means for subjecting the flow rate value to digital filter processing, and a stable flow rate calculating means for calculating a flow rate value by the filter processing means, digital filter processing is performed. As a result, arithmetic calculations equivalent to averaging can be performed without using a lot of data memory, and the filter characteristic can be changed by changing one variable called a filter coefficient. .

In addition, when the pulsation discriminating means determines a pulsation, there is a stable flow rate calculating means that calculates a stable value of the flow value by digital filter processing means. It is possible to perform filtering only during pulsation.

In addition, since the pulsation determination means determines whether or not the fluctuation range of the flow rate value is equal to or greater than a predetermined value, the filter process is changed according to the fluctuation range of the pulsation by determining based on the fluctuation range of the pulsation. can do.

In addition, the filter processing means is configured to change the filter characteristics according to the fluctuation range of the flow rate value.By changing the filter characteristics according to the fluctuation range, the filter characteristics gradually change with small fluctuations as the filter characteristics gradually change. it can At the same time, when the fluctuation is large, the fluctuation of the flow rate due to the pulsation can be largely suppressed by using a steep filter characteristic.

In addition, since the filter value is detected only when the flow rate detected by the instantaneous flow rate detection means is low, the filter process is performed only when the flow rate is low. The effect of pulsation at the time of flow can be greatly suppressed.

Also, since the filter processing means is configured to change the filter characteristics according to the flow rate value, by changing the filter characteristics according to the flow rate value, the filter processing is performed only at a low flow rate, so that the flow rate change at a large flow rate can be quickly performed. In addition to this, the effects of pulsation at low flow rates can be significantly reduced.

In addition, since the filter processing means is configured to change the filter characteristics according to the flow time interval of the instantaneous flow rate detection means, the filter characteristics are changed according to the flow rate detection time intervals, so that when the measurement interval is short. Is a gentle filter characteristic, and when the interval is wide, a steep filter characteristic can suppress the fluctuation. In addition, when the flow rate is large, the cutoff frequency of the filter characteristics is changed to be higher, and when the flow rate is low, the filter processing means is changed so that the cutoff frequency has a lower filter characteristic. In some cases, the responsiveness becomes faster, and pulsation can be suppressed at low flow rates.

In addition, since the filter characteristic is changed so that the fluctuation range of the flow rate value calculated by the stable flow rate calculation means is within a predetermined value, the filter characteristic is changed so that the fluctuation value is within the predetermined value. In addition, the flow rate fluctuation can always be suppressed to a predetermined value or less.

In addition, since the ultrasonic flowmeter that detects the flow rate by ultrasonic waves is used as the instantaneous flow rate detection means, the instantaneous flow rate can be measured even if a large flow rate fluctuation occurs by using the ultrasonic flowmeter. A stable flow rate can be obtained from the flow rate value by arithmetic. In addition, since the thermal flow meter is used as the instantaneous flow rate detection means, the instantaneous flow rate can be measured even if a large flow rate fluctuation occurs by using the thermal flow meter. A stable flow rate can be determined.

In addition, the control unit controls the periodicity changing means to change the cycle in the flow measurement in order so that the measurement cycle does not become constant, so that noise synchronized with the measurement cycle or the transmission cycle of ultrasonic waves is always received when receiving. Since they do not exist in the same phase and are dispersed, measurement errors can be reduced.

The control unit further includes a periodicity changing unit that sequentially changes a driving method of the drive circuit, wherein the control unit receives the output of the reception detection circuit so that the period does not become constant. Since the characteristic changing means is changed, the measurement can be performed by operating the period changing means with a plurality of settings in one flow measurement, so that the measurement result is a noise-dispersed and averaged result, and a stable measurement result can be obtained.

Further, the periodicity changing means is configured to output an output signal having a plurality of phases at the same frequency, and the control unit changes the phase setting of the output signal of the periodicity changing means for each measurement to drive the driving circuit. Since control is performed to change the phase, the reception detection timing can be changed by converting the phase fluctuation of the drive signal into time by changing the drive phase. For this reason, noise synchronized with the measurement cycle or the transmission cycle of the ultrasonic wave does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

Further, the frequency changing means may be configured to determine the first frequency, which is the operating frequency of the ultrasonic vibrator, and the first frequency. The control unit outputs the output signal obtained by changing the setting of the second frequency of the periodicity changing unit for each measurement via the drive circuit, with a configuration in which a signal of a second frequency different from the one frequency is superimposed and output. Therefore, the periodicity in the flow measurement can be disturbed. For this reason, noise synchronized with the measurement cycle or the transmission cycle of ultrasonic waves does not always exist in the same phase at the time of reception and is dispersed, so that the measurement error can be reduced.

Also, by measuring the time from reception detection to the next timer count-up / time by using the second time, measurement with higher resolution than the first time can be performed. Also, compared to a flow meter having the same resolution, the second timer only needs to be operated for a short time after the reception is detected, so that power consumption can be reduced.

In addition, since the second evening image is corrected by the first timer, the second evening image only needs to be stable for a short time, and there is no need to use special parts. Therefore, a high-resolution flowmeter can be easily realized.

In addition, when the output of the temperature sensor fluctuates more than the set value, the second timer is corrected by the first timer, so even if the operation of the second timer largely changes due to a change in temperature, It can be used.

In addition, when the output of the voltage sensor fluctuates more than the set value, the second timer is corrected by the first timer, so even if the operation of the second timer greatly changes due to the voltage change, it can be used. It is possible to do.

A flow measuring unit through which the fluid to be measured flows; a pair of ultrasonic transducers provided in the flow measuring unit for transmitting and receiving ultrasonic waves; and a driving circuit for driving one of the ultrasonic transducers A reception detection circuit that is connected to the other ultrasonic transducer and detects an ultrasonic signal; and a control unit that receives the output of the reception detection circuit and controls the drive circuit a predetermined number of times to drive the ultrasonic transducer again. A timer for measuring the elapsed time of the predetermined number of times, a calculation unit for calculating a flow rate from the output of the timer by calculation, and a periodicity stabilizing unit for sequentially changing a driving method of the drive circuit. The period stabilization means is controlled so that the measurement period is always constant. With this configuration, the measurement cycle is always constant even when the propagation time changes, so that the noise synchronized with the measurement cycle or the ultrasonic transmission cycle always has the same phase during reception regardless of the propagation time fluctuation. Therefore, the measurement error can be kept constant, and the flow measurement can be stabilized even with a very long noise period.

Further, the control unit has periodicity stabilizing means including a delay unit that can set a different delay time, and the control unit changes the output time of the drive circuit by switching the delay time. Since the measurement period is stabilized by changing the delay time, the measurement period can be stabilized without affecting the driving of the ultrasonic transducer.

In addition, since the control unit controls the drive circuit to keep the measurement time constant, the measurement cycle can be controlled to be constant by a simple calculation without calculating the propagation time of each ultrasonic wave. .

Claims

The scope of the claims

1. Transmission / reception means provided in the flow path for transmitting / receiving using a change in the state of the fluid, repetition means for repeating the signal propagation of the transmission / reception means, and propagation time of the state change during repetition by the repetition means And a flow rate detecting means for detecting a flow rate based on the value of the time measuring means, and a number changing means for changing the number of times to a predetermined number of repetitions.

2. The flowmeter according to claim 1, further comprising a pair of transmission / reception means using propagation of a sound wave as a change in the state of the fluid.

3. The method according to claim 1, further comprising a transmitting / receiving means using heat propagation as a change in the state of the fluid.

4. Elapsed time detecting means for detecting information on the way of the propagation time repeated by the repeating means, cycle detecting means for detecting the cycle of the flow rate variation from the information of the elapsed time detecting means, and detecting by the cycle detecting means. The flowmeter according to any one of claims 1 to 3, further comprising means for changing the number of times set to a measurement time that is approximately an integral multiple of the cycle.

5. The data holding means for holding the transmission / reception propagation time obtained by the elapsed time detecting means at least one kilometer or more, and comparing the data held by the data holding means with the measured propagation time data. 5. The flowmeter according to claim 4, further comprising a cycle detecting means for detecting a cycle by detecting.

6. The flow meter according to any one of claims 1 to 5, wherein the number-of-times changing means operates during predetermined processing.

7. The flowmeter according to claim 6, wherein the number changing means operates each time a predetermined flow rate is measured.

8. The flowmeter according to claim 6, wherein the number changing means is performed before the flow measurement processing.

9. The flowmeter according to claim 6, wherein the predetermined processing includes performing abnormality determination means for determining an abnormality in the flow rate from the flow rate measurement and flow rate management means for managing a usage state of the flow rate from the measured flow rate.

10. The flowmeter according to claim 4, wherein the number of repetitions according to the cycle obtained by the cycle detection means is used at the next flow rate measurement.

The flowmeter according to any one of claims 1 to 5, wherein the number-of-times changing means is operated when the measured flow rate is less than a predetermined flow rate.

12. A transmission / reception unit provided in the flow path for transmitting and receiving using a state change of the fluid, a time measurement unit for measuring a propagation time of the state change transmitted and received by the transmission / reception unit, and a flow rate based on the value of the time measurement unit A flowmeter comprising: a flow rate detecting means for detecting the fluctuation; a fluctuation detecting means for measuring a fluctuation in the flow path by the transmitting / receiving means; and a measurement control means for starting the measurement in synchronization with the fluctuation timing of the fluctuation detecting means. .

13. The flowmeter according to claim 12, further comprising a pair of transmission / reception means using propagation of a sound wave as a change in the state of the fluid.

13. The flowmeter according to claim 12, further comprising transmission / reception means using heat propagation as a fluid state change.

15. First and second vibrating means provided in the flow path for transmitting and receiving sound waves, switching means for switching the transmitting and receiving operations of the first and second vibrating means, and the first vibrating means A fluctuation detecting means for detecting a pressure fluctuation in the flow path of at least one of the first and second vibrating means; a time measuring means for measuring a propagation time of a sound wave transmitted and received by the first vibrating means and the second vibrating means; When the output of the detecting means has changed by a predetermined amount, the time measuring means measures a first time T 1 which propagates from the first vibrating means on the upstream side of the flow path to the second vibrating means on the downstream side, and the fluctuation detecting means When the output of the clock changes in reverse to the predetermined change, the timing control means measures the second time T2 transmitted from the second vibration means on the downstream side of the flow path to the first vibration means on the upstream side. Measurement control means to perform, and the first time measurement time T 1 Flowmeter according to claim 1 3, further comprising a flow detection means for calculating the flow rate using the second measured time T 2.

1 6. Start measurement of the first clocking time T1 when the output of the fluctuation detecting means changes by a predetermined amount, and start measuring the second clocking time T2 when the output of the fluctuation detecting means changes in the opposite direction to the predetermined change. In the measurement control to be started, and at the next measurement, when the output of the fluctuation detecting means changes in reverse to the predetermined change, the measurement of the first time T1 is started, and the output of the fluctuation detecting means changes by a predetermined amount. Measurement of the second clock time T2 is started when the measurement is started.The measurement control means performs the measurement control, and the measurement was performed using the previous first clock time T1 and the second clock time T2 while alternately changing the measurement start. The method according to claim 15, further comprising a flow rate detecting unit configured to calculate a flow rate by sequentially averaging the first flow rate and the second flow rate obtained using the next first time counting time T 1 and second time counting time T 2. Flow meter.

17. The flow meter according to any one of claims 12 to 16, further comprising a repetition means for performing transmission and reception a plurality of times.

1 8. Contracts with repetitive means for sending and receiving multiple times over an integral multiple of the The flowmeter according to claim 17.

19. A repetition means which starts transmission / reception measurement when the output of the fluctuation detection means changes by a predetermined amount, and repeatedly performs transmission / reception measurement until the output of the fluctuation detection means changes the same as the predetermined change. Flow meter according to clause 8.

20. A method according to any one of claims 12 and 15 to 19, further comprising selection means for switching between a case where the first vibration means and the second vibration means are used for transmitting and receiving sound waves and a case where they are used for detecting pressure fluctuation. Flow meter according to the item.

21. The flowmeter according to any one of claims 15 to 20, further comprising a fluctuation detecting means for detecting a vicinity of zero of an AC component of the fluctuation waveform.

22. A cycle detection means for detecting a cycle of a signal of the fluctuation detection means, and a measurement control means for starting measurement only when the cycle detected by the cycle detection means is a predetermined cycle. The flowmeter according to any one of the preceding items.

23. The flow meter according to any one of claims 15 to 22, further comprising a detection canceling means for automatically starting measurement after a predetermined time when a signal from the fluctuation detecting means cannot be detected.

24. The flow meter according to any one of claims 15 to 23, wherein the transmitting / receiving means, the first vibrating means, and the second vibrating means comprise a piezoelectric vibrator.

25. A transmitting / receiving unit provided in the flow path for transmitting and receiving using a change in the state of the fluid, a repeating unit for repeating the transmission and reception, and a propagation time during the repetition by the repeating unit is measured. A time measuring means for measuring, a flow rate detecting means for detecting a flow rate based on a value of the time measuring means, a fluctuation detecting means for detecting a fluid fluctuation in the flow path, a measurement control means for controlling the respective means, A flow meter comprising: a measurement monitoring unit that monitors an abnormality of each unit.

26. The flowmeter according to claim 25, further comprising a pair of transmission / reception means using propagation of a sound wave as a change in the state of the fluid.

27. The flowmeter according to claim 25, further comprising transmission / reception means using heat propagation as a change in the state of the fluid.

28. A pair of transmission / reception means provided in the flow path for transmitting / receiving a sound wave, a repetition means for repeating the signal transmission of the transmission / reception means, and measuring the propagation time of the sound wave during the repetition by the repetition means Time measuring means, flow rate detecting means for detecting a flow rate based on the value of the time measuring means, fluctuation detecting means for detecting fluid fluctuation in the flow path, measurement control means for controlling each of the means, and the measurement After the measurement instruction signal of the control means, a start signal instructing the start of sound wave transmission at the time of the first output signal of the fluctuation detecting means, and an end signal of instructing the end of repetition of transmission and reception of sound waves at the time of the second output signal of the fluctuation detecting means. 27. The flow meter according to claim 26, further comprising: a signal; and a measurement monitoring unit that monitors an abnormality of the start signal and the end signal.

29. The measurement monitoring means according to claim 28, further comprising a measurement monitoring means for instructing a start of transmission of a sound wave after a predetermined time when no start signal is generated within a predetermined time after the instruction of the measurement control means.

30. Equipped with a measurement monitoring means for instructing the start of sound wave transmission after a predetermined time if no start signal is generated within a predetermined time after the instruction of the measurement control means, and performing measurement at a predetermined number of repetitions. 29. The flowmeter according to claim 29.

31. The flowmeter according to claim 28, further comprising a measurement monitoring unit that does not perform measurement until the next instruction of the measurement control means when the start signal is not generated within a predetermined time after the instruction of the measurement control means. .

32. The flowmeter according to claim 28, further comprising a measurement monitoring means for terminating the reception of the sound wave when the end signal is not generated within a predetermined time after the start signal.

33. Claims 28 and 32 provided with measurement monitoring means for terminating the reception of the sound wave and outputting the start signal again when the end signal is not generated within a predetermined time after the start signal. The flow meter according to item 1.

34. The flowmeter according to claim 28, further comprising a measurement monitoring means for stopping transmission / reception processing when the number of repetitions becomes abnormal.

3.5.1 The first number of repetitions at the time of measurement, where data is transmitted from one transmitting / receiving means and received by the other transmitting / receiving means, and the other transmitting / receiving means is transmitting and receiving by one transmitting / receiving means 29. The flowmeter according to claim 28, further comprising: a measurement monitoring unit that compares the second number of repetitions at the time of measurement, and outputs a start signal again when the difference between the two repetitions is a predetermined number or more.

36. Among the pair of transmission / reception means, the first number of repetitions at the time of measurement transmitted from one transmission / reception means and received by the other transmission / reception means, and transmitted from the other transmission / reception means and received by one transmission / reception means 29. The flow meter according to claim 28, further comprising a repetition means for setting the second number of repetitions at the time of measurement to be performed to be the same.

37. The flowmeter according to claim 28, further comprising a measurement monitoring means for monitoring the number of times to output the start signal again up to a predetermined number of times and for preventing the repetition forever.

38. The flowmeter according to any one of claims 28 to 37, wherein a flow rate is measured from a reciprocal difference of a propagation time measured by repeating transmission and reception of ultrasonic waves a plurality of times.

39. Calculate the flow value using the instantaneous flow rate detecting means for detecting the instantaneous flow rate, the pulsation determining means for determining whether or not the flow rate value is pulsating, and means different depending on the determination result of the pulsation determining means. A flow meter provided with at least one or more stable flow rate calculating means.

40. A flowmeter comprising: an instantaneous flow rate detecting means for detecting an instantaneous flow rate; a filter processing means for digitally filtering a flow rate value; and a stable flow rate calculating means for calculating a flow rate value by the filter processing means.

41. The method according to any one of claims 39 and 40, further comprising a stable flow rate calculating means for calculating a stable value of the flow rate value by a digital filter processing means when the pulsation determining means determines that there is a pulsation. Flowmeter.

42. The flowmeter according to any one of claims 38 to 41, wherein the pulsation determination means determines whether or not the fluctuation range of the flow value is equal to or greater than a predetermined value.

43. The flowmeter according to any one of claims 39 to 42, wherein the filter processing means changes a filter characteristic according to a fluctuation range of the flow value.

44. The flowmeter according to any one of claims 39 to 43, wherein filtering is performed only when the flow rate value detected by the instantaneous flow rate detection means is low.

45. The filter processing means changes a filter characteristic according to a flow rate value.

39. The flow meter according to any one of items 9 to 4.

46. The flowmeter according to any one of claims 39 to 45, wherein the filter processing means changes the filter characteristics according to a measurement time interval of the instantaneous flow rate detection means.

47. A filter processing means for changing the cutoff frequency of one filter characteristic to be higher when the flow rate is large, and changing the cutoff frequency to have a lower filter characteristic when the flow rate is low. 4 6 Flowmeter described.

48. The flowmeter according to any one of claims 39 to 47, wherein the filter characteristic is changed so that a fluctuation range of the flow rate value calculated by the stable flow rate calculation means is within a predetermined value.

49. The flowmeter according to any one of claims 38 to 48, wherein an ultrasonic flowmeter that detects a flow rate by ultrasonic waves is used as instantaneous flow rate detection means.

50. The flowmeter according to any one of claims 38 to 48, wherein a thermal flowmeter is used as instantaneous flow rate detection means.

51. A flow rate measurement unit through which the fluid to be measured flows, a pair of ultrasonic transducers provided in the flow rate measurement unit for transmitting and receiving ultrasonic waves, a drive circuit for driving one ultrasonic transducer, and the other A reception detection circuit connected to the ultrasonic vibrator and detecting an ultrasonic pulse; a timer for measuring a propagation time of the ultrasonic pulse; a control unit for controlling the drive circuit; and a flow rate based on an output of the timer. And a periodicity changing means for sequentially changing the driving method of the drive circuit. A flow meter for controlling the periodicity changing means so as to sequentially change periods.

5 2. A flow rate measurement unit through which the fluid to be measured flows, a pair of ultrasonic transducers provided in the flow rate measurement unit for transmitting and receiving ultrasonic waves, a drive circuit for driving one ultrasonic transducer, and the other A reception detection circuit that is connected to the ultrasonic transducer and detects an ultrasonic pulse; a control unit that receives the output of the reception detection circuit and controls the drive circuit a predetermined number of times to drive the ultrasonic transducer again; A timer for measuring an elapsed time of a predetermined number of times, a calculation unit for calculating a flow rate from an output of the timer, and a periodicity change unit for sequentially changing a driving method of a drive circuit, wherein a control unit of the reception detection circuit A flowmeter which changes the periodicity changing means every time a reception is detected by the reception detection circuit upon receiving an output.

5 3. The periodicity changing means is configured to switch and output the output signals of a plurality of frequencies, and the control section controls the frequency setting of the periodicity changing means to change the driving frequency of the driving circuit for each measurement. The flowmeter according to claim 51 or 52.

5 4. The periodicity changing means is configured to output an output signal having a plurality of phases at the same frequency, and the control unit changes the phase setting of the output signal of the periodicity changing means for each measurement to drive the driving circuit. The flowmeter according to claim 51, wherein the flowmeter is controlled to change the phase.

55. The frequency changing means is configured to superimpose and output a signal of a first frequency, which is a frequency used by the ultrasonic vibrator, and a second frequency different from the first frequency. The flowmeter according to claim 51, wherein an output signal obtained by changing the setting of the second frequency of the changing means is output through the drive circuit.

56. The flowmeter according to claim 55, wherein the periodicity changing means switches between a setting with and without a second frequency.

57. The flowmeter according to claim 55, wherein the periodicity changing means changes the phase setting of the second frequency.

58. The flowmeter according to claim 55, wherein the periodicity changing means changes the frequency setting of the second frequency.

59. The flow rate according to claim 52, wherein the periodicity changing means includes a delay unit capable of setting different delay times, and the control unit changes the delay setting every time ultrasonic waves are transmitted or ultrasonic waves are detected. Total.

60. The flowmeter according to claim 51, wherein the width of the cycle changed by the cycle changing means is an integral multiple of a value corresponding to a propagation time variation due to a measurement error.

61. The flowmeter according to claim 51, wherein the width of the cycle changed by the cycle changing means is a cycle of a resonance frequency of the ultrasonic transducer.

62. The flowmeter according to claim 51, wherein the order of the pattern for changing the periodicity is the same for the measurement in the upstream direction and the measurement in the downstream direction.

63. The flowmeter according to claim 52, wherein the predetermined number is an integral multiple of the number of changes of the periodicity changing means.

6 4. A flow rate measurement unit through which the fluid to be measured flows, a pair of ultrasonic transducers provided in the flow rate measurement unit for transmitting and receiving ultrasonic waves, a drive circuit for driving one ultrasonic transducer, and the other A reception detection circuit connected to the ultrasonic transducer for detecting an ultrasonic pulse; A first timer for measuring the propagation time of the ultrasonic pulse, and a second timer for measuring the time from when the reception detection circuit detects the reception to when the value of the first image changes. A control unit that controls the drive circuit; and a calculation unit that obtains a flow rate by calculation from outputs of the first timer and the second timer, and corrects the second timer with the first timer. Flow meter with configuration.

65. The flowmeter according to claim 64, further comprising a temperature sensor, wherein the second evening image is corrected by the first evening image when the output of the temperature sensor changes by a set value or more.

66. The flowmeter according to claim 64, further comprising a voltage sensor, wherein the second evening time is corrected by the first evening time when the output of the voltage sensor changes by a set value or more.

6 7. A flow rate measurement unit through which the fluid to be measured flows, a pair of ultrasonic transducers provided in the flow rate measurement unit for transmitting and receiving ultrasonic waves, a drive circuit for driving one ultrasonic transducer, and the other A reception detection circuit that is connected to the ultrasonic vibrator and detects an ultrasonic pulse; a control unit that receives the output of the reception detection circuit and controls the drive circuit a predetermined number of times to drive the ultrasonic vibrator again; A timer for measuring a predetermined number of elapsed times, an arithmetic unit for calculating the flow rate from the output of the timer, and periodicity stabilizing means for sequentially changing a driving method of the drive circuit; A flow meter that controls the periodic stabilization means so that it is always constant.

68. The control device according to claim 67, wherein the control unit has a periodicity stabilizing means including a delay unit that can set a different delay time, and the control unit changes the output time of the drive circuit by switching the delay time. Flowmeter.

69. The control device according to claim 67, wherein the control unit controls the drive circuit so that the measurement time is constant. Flowmeter.